DragonDice

          """<b>Character State:</b>
/select [<i>NAME</i>] — Select the active character for the user who is asking.
/show|stat|state|stats — Display a summary of the active character's statistics.
/talk — Display the set of common languages for all the active characters selected in the conversation.
/heal <i>HP</i> — Restore <i>HP</i> hit points up to the maximum of the active character. 
/hurt|damage <i>HP</i> [, <i>DAMAGE</i>] — Deal <i>HP</i> damage to the active character. If a damage type is specified, the character's defenses may apply.
/bolster <i>HP</i> — Add temporary hit points to the active character.

/rest[ore] — Restore hit points to maximum and remove temporary hit points from the active character.
/gain <i>GP</i> — Add an amount of currency to the active character.
/spend <i>GP</i> — Remove an amount of currency to the active character.

<b>Hit Points:</b>
The <i>HP</i> argument to the health management commands may be a dice roll specification or a constant non-negative integer.

<b>Currency:</b>
................................................................................
/setrace <i>RACE</i> — Change the race of the active character. This operation does not work on imported characters.
/set ac =|+=|-= <i>N</i> — Change the armor class of the active character.
/set hp =|+=|-= <i>N</i> — Change the maximum hit points of the active character.
/set <i>SPEED</i> =|+=|-= <i>N</i> — Change a movement speed of the active character.
/set <i>ABILITY</i> =|+=|-= <i>N</i> — Change an ability score of the active character.
/addlevel <i>CLASS</i> [, <i>N</i>] — Add one or more levels in the given class to the active character. This operation does not work on imported characters.
/removelevel <i>CLASS</i> [, <i>N</i>] — Remove one or more levels in the given class to the active character. This operation does not work on imported characters.


/addproficiency <i>SKILL</i> [, <i>N</i>] — Add a proficiency in the given skill, optionally with a multiplier, to the active character. This operation does not work on imported characters.
/removeproficiency <i>SKILL</i> — Remove the proficiency in the given skill from the active character. This operation does not work on imported characters.
/set <i>SKILL</i> =|+=|-= <i>N</i> — Change a skill proficiency modifier of the active character.
/adddefense <i>DAMAGE</i>, <i>DEFENSE</i> — Add a defense against <i>DAMAGE</i> for the active character. <i>DEFENSE</i> may be a numerical factor or one of the adjectives <i>Normal</i>, <i>Immune</i>, <i>Invulnerable</i>, <i>Resistant</i>, <i>Vulnerable</i>.
/removedefense <i>DAMAGE</i> — Remove the defense against <i>DAMAGE</i> for the active character.
/set <i>SENSE</i> =|+=|-= <i>N</i> — Change a perception sense range of the active character.
/addlanguage <i>NAME</i> — Add a language proficiency to the active character.
................................................................................
          buffer.Append(", ").Append(HttpUtility.HtmlEncode chr.Profession) |> ignore
        buffer.Append("</i>\n\n")
          .Append("<b>Armor Class:</b> ").Append(chr.ArmorClass).Append('\n')
          .Append("<b>Hit Points:</b> ").Append(chr.CurrentHitPoints)
        |> ignore
        if chr.TemporaryHitPoints > 0 then
          buffer.Append(" + ").Append(chr.TemporaryHitPoints) |> ignore
        buffer.Append(" / ").Append(chr.MaxHitPoints).Append('\n')
          .Append("<b>Currency:</b> ").Append(Coin.toString chr.CurrentCoin).Append('\n')

        |> ignore

        let pos = buffer.Append("<b>Speed:</b> ").Length
        for KeyValue (speed, v) in chr.Speeds do
          if v > 0<ft/rnd> then
            if buffer.Length > pos then buffer.Append(", ") |> ignore
            buffer.Append(Speed.toString speed).Append(' ').Append(v).Append(" ft/rnd") |> ignore
        if buffer.Length = pos then buffer.Append("Immobile") |> ignore
        let pos = buffer.Append("\n\n").Length
................................................................................
        let buffer = Text.StringBuilder("<i>").Append(HttpUtility.HtmlEncode chr.Name).Append("</i> : HP - ").Append(hp)
        if f <> 1.0 then buffer.Append(" * ").Append(f) |> ignore
        buffer.Append(" → ").Append("<b>").Append(chr.CurrentHitPoints) |> ignore
        if chr.TemporaryHitPoints > 0 then
          buffer.Append(" + ").Append(chr.TemporaryHitPoints) |> ignore
        buffer.Append("</b> / ").Append(chr.MaxHitPoints) |> ignore
        return Markup (buffer.ToString(), List.empty)





















        
      | ["/rest" | "/restore"] ->
        let chr = selectedCharacter user
        chr.Rest()
        return Markup (
          sprintf "<i>%s</i> : HP = <b>%d</b>" (HttpUtility.HtmlEncode chr.Name) chr.CurrentHitPoints,
          List.empty
................................................................................
        let prof = Profession.ofString prof
        let count = int count
        chr.RemoveLevel(prof, count)
        return Markup (
          sprintf "<i>%s</i> : Profession = %s" (HttpUtility.HtmlEncode chr.Name) chr.Profession,
          List.empty
        )



























































      
      | ["/addproficiency" | "/removeproficiency"] ->
        return Markup (
          "<b>Note:</b> Select a skill proficiency",
          Skill.All
          |> Set.remove Skill.StrengthAttack
          |> Set.remove Skill.DexterityAttack

          """<b>Character State:</b>
/select [<i>NAME</i>] — Select the active character for the user who is asking.
/show|stat|state|stats — Display a summary of the active character's statistics.
/talk — Display the set of common languages for all the active characters selected in the conversation.
/heal <i>HP</i> — Restore <i>HP</i> hit points up to the maximum of the active character. 
/hurt|damage <i>HP</i> [, <i>DAMAGE</i>] — Deal <i>HP</i> damage to the active character. If a damage type is specified, the character's defenses may apply.
/bolster <i>HP</i> — Add temporary hit points to the active character.
/useslot <i>SL</i> — Use a level <i>SL</i> spell slot.
/rest[ore] — Restore hit points to maximum, remove temporary hit points, and restore spell slots for the active character.
/gain <i>GP</i> — Add an amount of currency to the active character.
/spend <i>GP</i> — Remove an amount of currency to the active character.

<b>Hit Points:</b>
The <i>HP</i> argument to the health management commands may be a dice roll specification or a constant non-negative integer.

<b>Currency:</b>
................................................................................
/setrace <i>RACE</i> — Change the race of the active character. This operation does not work on imported characters.
/set ac =|+=|-= <i>N</i> — Change the armor class of the active character.
/set hp =|+=|-= <i>N</i> — Change the maximum hit points of the active character.
/set <i>SPEED</i> =|+=|-= <i>N</i> — Change a movement speed of the active character.
/set <i>ABILITY</i> =|+=|-= <i>N</i> — Change an ability score of the active character.
/addlevel <i>CLASS</i> [, <i>N</i>] — Add one or more levels in the given class to the active character. This operation does not work on imported characters.
/removelevel <i>CLASS</i> [, <i>N</i>] — Remove one or more levels in the given class to the active character. This operation does not work on imported characters.
/addslot <i>SL</i> [, <i>N</i>] — Add one or more spell slots of the given level to the active character.
/removeslot <i>SL</i> [, <i>N</i>] — Add one or more spell slots of the given level to the active character.
/addproficiency <i>SKILL</i> [, <i>N</i>] — Add a proficiency in the given skill, optionally with a multiplier, to the active character. This operation does not work on imported characters.
/removeproficiency <i>SKILL</i> — Remove the proficiency in the given skill from the active character. This operation does not work on imported characters.
/set <i>SKILL</i> =|+=|-= <i>N</i> — Change a skill proficiency modifier of the active character.
/adddefense <i>DAMAGE</i>, <i>DEFENSE</i> — Add a defense against <i>DAMAGE</i> for the active character. <i>DEFENSE</i> may be a numerical factor or one of the adjectives <i>Normal</i>, <i>Immune</i>, <i>Invulnerable</i>, <i>Resistant</i>, <i>Vulnerable</i>.
/removedefense <i>DAMAGE</i> — Remove the defense against <i>DAMAGE</i> for the active character.
/set <i>SENSE</i> =|+=|-= <i>N</i> — Change a perception sense range of the active character.
/addlanguage <i>NAME</i> — Add a language proficiency to the active character.
................................................................................
          buffer.Append(", ").Append(HttpUtility.HtmlEncode chr.Profession) |> ignore
        buffer.Append("</i>\n\n")
          .Append("<b>Armor Class:</b> ").Append(chr.ArmorClass).Append('\n')
          .Append("<b>Hit Points:</b> ").Append(chr.CurrentHitPoints)
        |> ignore
        if chr.TemporaryHitPoints > 0 then
          buffer.Append(" + ").Append(chr.TemporaryHitPoints) |> ignore
        buffer.Append(" / ").Append(chr.MaxHitPoints).Append('\n') |> ignore
        if chr.MaxSlots.Values |> Seq.max > 0 then
          buffer.Append("<b>Spell Slots:</b> ").Append(Slot.toSummary chr.MaxSlots chr.CurrentSlots).Append('\n')
          |> ignore
        buffer.Append("<b>Currency:</b> ").Append(Coin.toString chr.CurrentCoin).Append('\n') |> ignore
        let pos = buffer.Append("<b>Speed:</b> ").Length
        for KeyValue (speed, v) in chr.Speeds do
          if v > 0<ft/rnd> then
            if buffer.Length > pos then buffer.Append(", ") |> ignore
            buffer.Append(Speed.toString speed).Append(' ').Append(v).Append(" ft/rnd") |> ignore
        if buffer.Length = pos then buffer.Append("Immobile") |> ignore
        let pos = buffer.Append("\n\n").Length
................................................................................
        let buffer = Text.StringBuilder("<i>").Append(HttpUtility.HtmlEncode chr.Name).Append("</i> : HP - ").Append(hp)
        if f <> 1.0 then buffer.Append(" * ").Append(f) |> ignore
        buffer.Append(" → ").Append("<b>").Append(chr.CurrentHitPoints) |> ignore
        if chr.TemporaryHitPoints > 0 then
          buffer.Append(" + ").Append(chr.TemporaryHitPoints) |> ignore
        buffer.Append("</b> / ").Append(chr.MaxHitPoints) |> ignore
        return Markup (buffer.ToString(), List.empty)

      | ["/useslot"] ->
        let chr = selectedCharacter user
        let buttons = [
          for KeyValue (slot, n) in chr.CurrentSlots do
            if n > 0 then yield sprintf "%c (x%d)" (Slot.positiveSymbol slot) n, Slot.toString slot
        ]
        if List.isEmpty buttons then failwith "No spell slots available"
        return Markup (
          "<b>Note:</b> Select spell slot to use",
          List.singleton buttons
        )

      | ["/useslot"; slot] ->
        let chr = selectedCharacter user
        let slot = Slot.ofString slot
        chr.UseSlot(slot)
        return Markup (
          sprintf "<i>%s</i> : Spell Slots = <b>%s</b>" (HttpUtility.HtmlEncode chr.Name) (Slot.toSummary chr.MaxSlots chr.CurrentSlots),
          List.empty
        )
        
      | ["/rest" | "/restore"] ->
        let chr = selectedCharacter user
        chr.Rest()
        return Markup (
          sprintf "<i>%s</i> : HP = <b>%d</b>" (HttpUtility.HtmlEncode chr.Name) chr.CurrentHitPoints,
          List.empty
................................................................................
        let prof = Profession.ofString prof
        let count = int count
        chr.RemoveLevel(prof, count)
        return Markup (
          sprintf "<i>%s</i> : Profession = %s" (HttpUtility.HtmlEncode chr.Name) chr.Profession,
          List.empty
        )
        
      | ["/addslot" | "/removeslot"] ->
        return Markup (
          "<b>Note:</b> Select spell slot level",
          [
            for i = 1 to 3 do
              yield [
                for j = 1 to 3 do
                  let slot = enum<Slot>(i * j)
                  yield Slot.positiveSymbol slot |> string, Slot.toString slot
              ]
          ]
        )

      | ["/addslot"; slot] ->
        let chr = selectedCharacter user
        let slot = Slot.ofString slot
        chr.MaxSlots <-
          let slots = chr.MaxSlots
          slots.With[slot, slots.[slot] + 1]
        return Markup (
          sprintf "<i>%s</i> : Spell Slots = <b>%s</b>" (HttpUtility.HtmlEncode chr.Name) (Slot.toSummary chr.MaxSlots chr.CurrentSlots),
          List.empty
        )

      | ["/addslot"; slot; count] ->
        let chr = selectedCharacter user
        let slot = Slot.ofString slot
        let count = int count
        chr.MaxSlots <-
          let slots = chr.MaxSlots
          slots.With[slot, max 0 (slots.[slot] + count)]
        return Markup (
          sprintf "<i>%s</i> : Spell Slots = <b>%s</b>" (HttpUtility.HtmlEncode chr.Name) (Slot.toSummary chr.MaxSlots chr.CurrentSlots),
          List.empty
        )

      | ["/removeslot"; slot] ->
        let chr = selectedCharacter user
        let slot = Slot.ofString slot
        chr.MaxSlots <-
          let slots = chr.MaxSlots
          slots.With[slot, max 0 (slots.[slot] - 1)]
        return Markup (
          sprintf "<i>%s</i> : Spell Slots = <b>%s</b>" (HttpUtility.HtmlEncode chr.Name) (Slot.toSummary chr.MaxSlots chr.CurrentSlots),
          List.empty
        )

      | ["/removeslot"; slot; count] ->
        let chr = selectedCharacter user
        let slot = Slot.ofString slot
        let count = int count
        chr.MaxSlots <-
          let slots = chr.MaxSlots
          slots.With[slot, max 0 (slots.[slot] - count)]
        return Markup (
          sprintf "<i>%s</i> : Spell Slots = <b>%s</b>" (HttpUtility.HtmlEncode chr.Name) (Slot.toSummary chr.MaxSlots chr.CurrentSlots),
          List.empty
        )
      
      | ["/addproficiency" | "/removeproficiency"] ->
        return Markup (
          "<b>Note:</b> Select a skill proficiency",
          Skill.All
          |> Set.remove Skill.StrengthAttack
          |> Set.remove Skill.DexterityAttack

      ResizeArray<IStatLayer>(2)

  let mutable stats : Option<StatBlock> = None
  
  let mutable currentHitPoints = 0
  let mutable temporaryHitPoints = 0
  


  let mutable currentCoin = 0m<gp>
  
  let mutable fullPath =
    let path = defaultArg path String.Empty
    if not (String.IsNullOrEmpty path) then
      IO.Path.GetFullPath(path)
    else
................................................................................
  /// Get the character's hit point maximum from the stat block or set it in the first custom stat layer.
  member this.MaxHitPoints
    with get () = this.StatBlock.MaxHitPoints
    and set v =
      let v0 = this.StatBlock.MaxHitPoints
      let sl = this.GetOrAddStatLayer<CustomStatLayer>()
      sl.MaxHitPoints <- sl.MaxHitPoints + v - v0











  /// Get the character's size from the stat block.
  member this.Size = this.StatBlock.Size

  /// Get the character's speeds from the stat block or set them in the first custom stat layer.
  member this.Speeds
    with get () = this.StatBlock.Speeds
................................................................................
  
  /// Remove a language in the first custom stat layer.
  member this.RemoveLanguage(lang:Language) =
    let sl = this.GetOrAddStatLayer<CustomStatLayer>()
    sl.Languages <- Set.remove lang sl.Languages

  /// Get the character's level from the stat block.
  member this.Level = this.StatBlock.Level
  
  /// Get the character's proficiency bonus from the stat block.
  member this.ProficiencyBonus = this.StatBlock.ProficiencyBonus
  
  /// Add one or more levels in the given profession to the character.
  member this.AddLevel(profession:Profession, ?count:int) =
    let count = defaultArg count 1
................................................................................
  /// Temporary hit points of the character.
  member __.TemporaryHitPoints = temporaryHitPoints
    
  /// Give the character temporary hit points.
  /// Sets the temporary hit points of the character to the maximum of its current value or the given value.
  member this.AddTemporaryHitPoints(hp:int) =
    temporaryHitPoints <- max temporaryHitPoints hp
  









  /// Apply the effects of a full rest.
  /// Restores current hit points to the character's maximum and removes all temporary hit points.

  member this.Rest() =

    currentHitPoints <- this.StatBlock.MaxHitPoints
    temporaryHitPoints <- 0

    
  /// Amount of currency in the character's bank account.
  member __.CurrentCoin = currentCoin
  
  /// Add some gold to the character's bank account.
  member __.Gain(gp:decimal<gp>) =
    if gp < 0m<gp> then invalidArg "gp" "Currency amount must be non-negative"
................................................................................
    stats <- None
    
    do
      let layer = Open5eStatLayer()
      layer.SetJson(object)
      layers.Add(layer)
      
    currentHitPoints <- this.MaxHitPoints
    temporaryHitPoints <- 0

    currentCoin <- 0m<gp>

  /// Deserialize the character from an XML representation.
  member this.SetXml(element:XElement) =
    layers.Clear()
    stats <- None
    
................................................................................
    }
    
    temporaryHitPoints <- query {
      for it in element.Descendants(XNamespace.None + "TemporaryHitPoints") do
      select (int <| it.Value.Trim())
      exactlyOneOrDefault
    }





    
    currentCoin <- query {
      for it in element.Descendants(XNamespace.None + "CurrentCoin") do
      select (Coin.ofString <| it.Value.Trim())
      exactlyOneOrDefault
    }
    
................................................................................
    let element = XElement(XNamespace.None + "Character")
    
    for layer in layers do
      element.Add(layer.GetXml())
      
    element.Add(XElement(XNamespace.None + "CurrentHitPoints", string currentHitPoints))
    element.Add(XElement(XNamespace.None + "TemporaryHitPoints", string temporaryHitPoints))





    
    element.Add(XElement(XNamespace.None + "CurrentCoin", Coin.toString currentCoin))
    
    element

  /// File path where the character is stored.
  member __.FullPath = fullPath

      ResizeArray<IStatLayer>(2)

  let mutable stats : Option<StatBlock> = None
  
  let mutable currentHitPoints = 0
  let mutable temporaryHitPoints = 0
  
  let mutable currentSlots = EnumMap<Slot, int>()
  
  let mutable currentCoin = 0m<gp>
  
  let mutable fullPath =
    let path = defaultArg path String.Empty
    if not (String.IsNullOrEmpty path) then
      IO.Path.GetFullPath(path)
    else
................................................................................
  /// Get the character's hit point maximum from the stat block or set it in the first custom stat layer.
  member this.MaxHitPoints
    with get () = this.StatBlock.MaxHitPoints
    and set v =
      let v0 = this.StatBlock.MaxHitPoints
      let sl = this.GetOrAddStatLayer<CustomStatLayer>()
      sl.MaxHitPoints <- sl.MaxHitPoints + v - v0

  /// Get the character's spell slots from the stat block or set them in the first custom stat layer.
  member this.MaxSlots
    with get () = this.StatBlock.MaxSlots
    and set v =
      let v0 = this.StatBlock.MaxSlots
      let sl = this.GetOrAddStatLayer<CustomStatLayer>()
      sl.MaxSlots <-
        EnumMap.map2Values (-) v v0
        |> EnumMap.map2Values (+) sl.MaxSlots

  /// Get the character's size from the stat block.
  member this.Size = this.StatBlock.Size

  /// Get the character's speeds from the stat block or set them in the first custom stat layer.
  member this.Speeds
    with get () = this.StatBlock.Speeds
................................................................................
  
  /// Remove a language in the first custom stat layer.
  member this.RemoveLanguage(lang:Language) =
    let sl = this.GetOrAddStatLayer<CustomStatLayer>()
    sl.Languages <- Set.remove lang sl.Languages

  /// Get the character's level from the stat block.
  member this.Level = this.StatBlock.TotalLevel
  
  /// Get the character's proficiency bonus from the stat block.
  member this.ProficiencyBonus = this.StatBlock.ProficiencyBonus
  
  /// Add one or more levels in the given profession to the character.
  member this.AddLevel(profession:Profession, ?count:int) =
    let count = defaultArg count 1
................................................................................
  /// Temporary hit points of the character.
  member __.TemporaryHitPoints = temporaryHitPoints
    
  /// Give the character temporary hit points.
  /// Sets the temporary hit points of the character to the maximum of its current value or the given value.
  member this.AddTemporaryHitPoints(hp:int) =
    temporaryHitPoints <- max temporaryHitPoints hp
    
  /// Currently available spell slots of the character.
  member __.CurrentSlots = currentSlots
  
  /// Use a spell slot of the given level.
  member __.UseSlot(slot:Slot) =
    let n = currentSlots.[slot]
    if n <= 0 then failwith "No spell slot of the given level available"
    currentSlots <- currentSlots.With[slot, n - 1]
  
  /// Apply the effects of a full rest.
  /// Restores current hit points to the character's maximum, removes all temporary hit points,
  /// restores all spell slots.
  member this.Rest() =
    let stats = this.StatBlock
    currentHitPoints <- stats.MaxHitPoints
    temporaryHitPoints <- 0
    currentSlots <- stats.MaxSlots
    
  /// Amount of currency in the character's bank account.
  member __.CurrentCoin = currentCoin
  
  /// Add some gold to the character's bank account.
  member __.Gain(gp:decimal<gp>) =
    if gp < 0m<gp> then invalidArg "gp" "Currency amount must be non-negative"
................................................................................
    stats <- None
    
    do
      let layer = Open5eStatLayer()
      layer.SetJson(object)
      layers.Add(layer)
      
    this.Rest()


    currentCoin <- 0m<gp>

  /// Deserialize the character from an XML representation.
  member this.SetXml(element:XElement) =
    layers.Clear()
    stats <- None
    
................................................................................
    }
    
    temporaryHitPoints <- query {
      for it in element.Descendants(XNamespace.None + "TemporaryHitPoints") do
      select (int <| it.Value.Trim())
      exactlyOneOrDefault
    }
    
    currentSlots <- query {
      for it in element.Descendants(XNamespace.None + "CurrentSlots") do
      select (Slot.ofString <| it.Attribute(XNamespace.None + "Level").Value, int <| it.Value)
    } |> EnumMap
    
    currentCoin <- query {
      for it in element.Descendants(XNamespace.None + "CurrentCoin") do
      select (Coin.ofString <| it.Value.Trim())
      exactlyOneOrDefault
    }
    
................................................................................
    let element = XElement(XNamespace.None + "Character")
    
    for layer in layers do
      element.Add(layer.GetXml())
      
    element.Add(XElement(XNamespace.None + "CurrentHitPoints", string currentHitPoints))
    element.Add(XElement(XNamespace.None + "TemporaryHitPoints", string temporaryHitPoints))
    
    for KeyValue (slot, v) in currentSlots do
      element.Add(
        XElement(XNamespace.None + "CurrentSlots", XAttribute(XNamespace.None + "Level", Slot.toString slot), string v)
      )
    
    element.Add(XElement(XNamespace.None + "CurrentCoin", Coin.toString currentCoin))
    
    element

  /// File path where the character is stored.
  member __.FullPath = fullPath

  member val Name : Option<string> = None with get, set

  /// Difficulty class of attacks against the character. Added to existing value when applied.
  member val ArmorClass = 0 with get, set

  /// Natural hit point maximum of the character. Added to existing value when applied.
  member val MaxHitPoints = 0 with get, set




  /// Movements speeds of the character. Added to existing values when applied.
  member val Speeds = EnumMap<Speed, int<ft/rnd>>() with get, set

  /// Ability scores of the character. Added to existing values when applied.
  member val Abilities = EnumMap<Ability, int>() with get, set

................................................................................
    }

    this.MaxHitPoints <- query {
      for it in element.Descendants(XNamespace.None + "MaxHitPoints") do
      select (int <| it.Value.Trim())
      exactlyOneOrDefault
    }





    
    this.Speeds <- query {
      for it in element.Descendants(XNamespace.None + "Speed") do
      select (Speed.ofString <| it.Attribute(XNamespace.None + "Name").Value, int(it.Value.Trim()) * 1<ft/rnd>)
    } |> EnumMap

    this.Abilities <- query {
................................................................................
    | None   -> ()

    if this.ArmorClass <> 0 then
      element.Add(XElement(XNamespace.None + "ArmorClass", sprintf "%+d" this.ArmorClass))

    if this.MaxHitPoints <> 0 then
      element.Add(XElement(XNamespace.None + "MaxHitPoints", sprintf "%+d" this.MaxHitPoints))









    this.Speeds
    |> Seq.iter (fun (KeyValue (speed, v)) ->
      if v <> 0<ft/rnd> then
        element.Add(
          XElement(XNamespace.None + "Speed", XAttribute(XNamespace.None + "Name", Speed.toString speed), sprintf "%+d" v)
        )
................................................................................
    | Some v -> stats <- { stats with Name = v }
    | None   -> ()

    stats <- {
      stats with
        ArmorClass = stats.ArmorClass + this.ArmorClass
        MaxHitPoints = stats.MaxHitPoints + this.MaxHitPoints

        Abilities = EnumMap.map2Values (+) stats.Abilities this.Abilities
        Speeds = EnumMap.map2Values (+) stats.Speeds this.Speeds
        Defenses = List.append this.Defenses stats.Defenses
        Skills = EnumMap.map2Values (+) stats.Skills this.Skills
        Senses = EnumMap.map2Values max stats.Senses this.Senses
        Languages = Set.union stats.Languages this.Languages
    }

  member val Name : Option<string> = None with get, set

  /// Difficulty class of attacks against the character. Added to existing value when applied.
  member val ArmorClass = 0 with get, set

  /// Natural hit point maximum of the character. Added to existing value when applied.
  member val MaxHitPoints = 0 with get, set
  
  /// Total spell slots available to the character. Added to existing value when applied.
  member val MaxSlots = EnumMap<Slot, int>() with get, set

  /// Movements speeds of the character. Added to existing values when applied.
  member val Speeds = EnumMap<Speed, int<ft/rnd>>() with get, set

  /// Ability scores of the character. Added to existing values when applied.
  member val Abilities = EnumMap<Ability, int>() with get, set

................................................................................
    }

    this.MaxHitPoints <- query {
      for it in element.Descendants(XNamespace.None + "MaxHitPoints") do
      select (int <| it.Value.Trim())
      exactlyOneOrDefault
    }
    
    this.MaxSlots <- query {
      for it in element.Descendants(XNamespace.None + "MaxSlots") do
      select (Slot.ofString <| it.Attribute(XNamespace.None + "Level").Value, int <| it.Value.Trim())
    } |> EnumMap
    
    this.Speeds <- query {
      for it in element.Descendants(XNamespace.None + "Speed") do
      select (Speed.ofString <| it.Attribute(XNamespace.None + "Name").Value, int(it.Value.Trim()) * 1<ft/rnd>)
    } |> EnumMap

    this.Abilities <- query {
................................................................................
    | None   -> ()

    if this.ArmorClass <> 0 then
      element.Add(XElement(XNamespace.None + "ArmorClass", sprintf "%+d" this.ArmorClass))

    if this.MaxHitPoints <> 0 then
      element.Add(XElement(XNamespace.None + "MaxHitPoints", sprintf "%+d" this.MaxHitPoints))

    this.MaxSlots
    |> Seq.iter (fun (KeyValue (slot, v)) ->
      if v <> 0 then
        element.Add(
          XElement(XNamespace.None + "MaxSlots", XAttribute(XNamespace.None + "Level", Slot.toString slot), sprintf "%+d" v)
        )
    )

    this.Speeds
    |> Seq.iter (fun (KeyValue (speed, v)) ->
      if v <> 0<ft/rnd> then
        element.Add(
          XElement(XNamespace.None + "Speed", XAttribute(XNamespace.None + "Name", Speed.toString speed), sprintf "%+d" v)
        )
................................................................................
    | Some v -> stats <- { stats with Name = v }
    | None   -> ()

    stats <- {
      stats with
        ArmorClass = stats.ArmorClass + this.ArmorClass
        MaxHitPoints = stats.MaxHitPoints + this.MaxHitPoints
        MaxSlots = EnumMap.map2Values (+) stats.MaxSlots this.MaxSlots
        Abilities = EnumMap.map2Values (+) stats.Abilities this.Abilities
        Speeds = EnumMap.map2Values (+) stats.Speeds this.Speeds
        Defenses = List.append this.Defenses stats.Defenses
        Skills = EnumMap.map2Values (+) stats.Skills this.Skills
        Senses = EnumMap.map2Values max stats.Senses this.Senses
        Languages = Set.union stats.Languages this.Languages
    }

    let addArmorClass =
      Ability.modifier stats.Abilities.[Ability.Dexterity]
      |> match this.MaxArmorClassModifier with Some v -> min v | None -> id

    let addHitPoints =
      Ability.modifier stats.Abilities.[Ability.Constitution]
      |> (+) (if Race.tryParse stats.Race = Some Race.HillDwarf then 1 else 0)
      |> (*) stats.Level

    { stats with
        ArmorClass = stats.ArmorClass + addArmorClass
        MaxHitPoints = stats.MaxHitPoints + addHitPoints

        Skills = stats.Skills |> EnumMap.mapValues ((*) stats.ProficiencyBonus)
    }

  interface IStatLayer with
    override this.SetXml(element) = this.SetXml(element)
    override this.GetXml() = this.GetXml()
    override this.Priority = 0xF0
    override this.Apply(stats) = this.Apply(stats)

    let addArmorClass =
      Ability.modifier stats.Abilities.[Ability.Dexterity]
      |> match this.MaxArmorClassModifier with Some v -> min v | None -> id

    let addHitPoints =
      Ability.modifier stats.Abilities.[Ability.Constitution]
      |> (+) (if Race.tryParse stats.Race = Some Race.HillDwarf then 1 else 0)
      |> (*) stats.TotalLevel

    { stats with
        ArmorClass = stats.ArmorClass + addArmorClass
        MaxHitPoints = stats.MaxHitPoints + addHitPoints
        MaxSlots = stats.MaxSlots |> EnumMap.map2Values (+) (Slot.ofLevel stats.CasterLevel)
        Skills = stats.Skills |> EnumMap.mapValues ((*) stats.ProficiencyBonus)
    }

  interface IStatLayer with
    override this.SetXml(element) = this.SetXml(element)
    override this.GetXml() = this.GetXml()
    override this.Priority = 0xF0
    override this.Apply(stats) = this.Apply(stats)

    <Compile Include="Speed.fs" />
    <Compile Include="Damage.fs" />
    <Compile Include="Defense.fs" />
    <Compile Include="Sense.fs" />
    <Compile Include="EnumMap.fs" />
    <Compile Include="Race.fs" />
    <Compile Include="Profession.fs" />

    <Compile Include="StatBlock.fs" />
    <Compile Include="LRUCache.fs" />
    <Compile Include="BasicStatLayer.fs" />
    <Compile Include="Open5eStatLayer.fs" />
    <Compile Include="LevelStatLayer.fs" />
    <Compile Include="DerivedStatLayer.fs" />
    <Compile Include="CustomStatLayer.fs" />

    <Compile Include="Speed.fs" />
    <Compile Include="Damage.fs" />
    <Compile Include="Defense.fs" />
    <Compile Include="Sense.fs" />
    <Compile Include="EnumMap.fs" />
    <Compile Include="Race.fs" />
    <Compile Include="Profession.fs" />
    <Compile Include="Slot.fs" />
    <Compile Include="StatBlock.fs" />
    <Compile Include="LRUCache.fs" />
    <Compile Include="BasicStatLayer.fs" />
    <Compile Include="Open5eStatLayer.fs" />
    <Compile Include="LevelStatLayer.fs" />
    <Compile Include="DerivedStatLayer.fs" />
    <Compile Include="CustomStatLayer.fs" />

    element
  
  /// Apply all defined customizations to the given character stats.
  member this.Apply(stats:StatBlock) =
    let profession =
      (if String.IsNullOrEmpty stats.Profession then String.Empty else ", ") +
      sprintf "%O (%d)" this.Profession this.Count

    let hitDice =
      Profession.hitDice this.Profession

    let addHitPoints =
      let count, init = if stats.Level = 0 then this.Count - 1, hitDice.Maximum else this.Count, 0
      init + count * int(ceil <| Dice.estimate hitDice)


































    { stats with
        Profession = stats.Profession + profession
        MaxHitPoints = stats.MaxHitPoints + addHitPoints

        Skills = EnumMap.map2Values max stats.Skills <| Profession.proficiencies this.Profession
        Level = stats.Level + this.Count

    }

  interface IStatLayer with
    override this.SetXml(element) = this.SetXml(element)
    override this.GetXml() = this.GetXml()
    override this.Priority = 0x10
    override this.Apply(stats) = this.Apply(stats)

    element
  
  /// Apply all defined customizations to the given character stats.
  member this.Apply(stats:StatBlock) =
    let profession =
      (if String.IsNullOrEmpty stats.Profession then String.Empty else ", ") +
      sprintf "%O (%d)" this.Profession this.Count

    let hitDice =
      Profession.hitDice this.Profession

    let addHitPoints =
      let count, init = if stats.TotalLevel = 0 then this.Count - 1, hitDice.Maximum else this.Count, 0
      init + count * int(ceil <| Dice.estimate hitDice)
      
    let addSlots =
      if this.Profession = Profession.Warlock then
        let slot =
          if   this.Count >=  9 then Slot.Level5
          elif this.Count >=  7 then Slot.Level4
          elif this.Count >=  5 then Slot.Level3
          elif this.Count >=  3 then Slot.Level2
          else                       Slot.Level1
        let n =
          if   this.Count >= 17 then 4
          elif this.Count >= 11 then 3
          elif this.Count >=  2 then 2
          elif this.Count >=  1 then 1
          else                       0
        EnumMap[slot, n]
      else
        EnumMap()

    let addCasterLevel =
      match this.Profession with
      | Profession.Alchemist
      | Profession.Bard
      | Profession.Cleric
      | Profession.Druid
      | Profession.Sorcerer
      | Profession.Wizard ->
        this.Count
      | Profession.Paladin
      | Profession.Ranger ->
        this.Count / 2
      | _ ->
        0

    { stats with
        Profession = stats.Profession + profession
        MaxHitPoints = stats.MaxHitPoints + addHitPoints
        MaxSlots = EnumMap.map2Values (+) stats.MaxSlots addSlots
        Skills = EnumMap.map2Values max stats.Skills <| Profession.proficiencies this.Profession
        TotalLevel = stats.TotalLevel + this.Count
        CasterLevel = stats.CasterLevel + addCasterLevel
    }

  interface IStatLayer with
    override this.SetXml(element) = this.SetXml(element)
    override this.GetXml() = this.GetXml()
    override this.Priority = 0x10
    override this.Apply(stats) = this.Apply(stats)

/// Base layer for monster stats imported from Open5e.
type Open5eStatLayer() =
  static let SemicolonPattern = Regex(@"\s*;\s*", RegexOptions.CultureInvariant)
  static let CommaPattern = Regex(@"\s*,\s*(?:and\s+)?", RegexOptions.CultureInvariant ||| RegexOptions.IgnoreCase)
  static let RangePattern = Regex(@"^(.+)\s+(\d+)\s+ft\.?$", RegexOptions.CultureInvariant)
  static let NonMagicalPattern = Regex(@"\s+from\s+non-?magical\b", RegexOptions.CultureInvariant)
  static let SpellcastingPattern = Regex(@"\bspellcasting\s+ability\s+is\s+(\w+)\s+\(spell\s+save\s+DC\s+(\d+)\)", RegexOptions.CultureInvariant ||| RegexOptions.IgnoreCase)

  
  static let parseStats (stats:JObject) : StatBlock =
    let name = stats.["name"].ToObject<string>()
    let typ = stats.["type"].ToObject<string>() |> CultureInfo.InvariantCulture.TextInfo.ToTitleCase
    let subtype = stats.["subtype"].ToObject<string>() |> CultureInfo.InvariantCulture.TextInfo.ToTitleCase
    let ac = stats.["armor_class"].ToObject<int>()
    let hp = stats.["hit_points"].ToObject<int>()
    let size = stats.["size"].ToObject<Size>()
    let level = stats.["challenge_rating"].ToObject<int>()






    let prof = (level + 3) / 4 + 1

    let speeds =
      stats.["speed"].ToObject<JObject>().Properties()
      |> Seq.map (fun it -> Speed.ofString it.Path, it.Value.ToObject<int<ft/rnd>>())
      |> EnumMap

................................................................................
        | _ ->
          ()
              
        yield Skill.StrengthAttack, prof
        yield Skill.DexterityAttack, prof
      }
      |> EnumMap















      
    let senses =
      (
        match stats.TryGetValue("senses") with
        | true, it when it.Type <> JTokenType.Null ->
          it.ToObject<string>()
          |> CommaPattern.Split
................................................................................
    
    {
      Name = name
      Race = if not (String.IsNullOrEmpty subtype) then sprintf "%s (%s)" typ subtype else typ
      Profession = String.Empty
      ArmorClass = ac
      MaxHitPoints = hp

      Size = size
      Speeds = speeds
      Abilities = abilities
      Defenses = defenses
      Skills = skills
      Senses = senses
      Languages = languages
      Level = level

    }
    
  static let cache = LRUCache<string, StatBlock>(1024)

  let mutable slug = "commoner"
  let mutable stats : Option<StatBlock> = None

/// Base layer for monster stats imported from Open5e.
type Open5eStatLayer() =
  static let SemicolonPattern = Regex(@"\s*;\s*", RegexOptions.CultureInvariant)
  static let CommaPattern = Regex(@"\s*,\s*(?:and\s+)?", RegexOptions.CultureInvariant ||| RegexOptions.IgnoreCase)
  static let RangePattern = Regex(@"^(.+)\s+(\d+)\s+ft\.?$", RegexOptions.CultureInvariant)
  static let NonMagicalPattern = Regex(@"\s+from\s+non-?magical\b", RegexOptions.CultureInvariant)
  static let SpellcastingPattern = Regex(@"\bspellcasting\s+ability\s+is\s+(\w+)\s+\(spell\s+save\s+DC\s+(\d+)\)", RegexOptions.CultureInvariant ||| RegexOptions.IgnoreCase)
  static let SpellcasterPattern = Regex(@"\bis\s+a\s+(\d+)(?:st|nd|rd)[-\s]level\s+spellcaster\b", RegexOptions.CultureInvariant ||| RegexOptions.IgnoreCase)
  
  static let parseStats (stats:JObject) : StatBlock =
    let name = stats.["name"].ToObject<string>()
    let typ = stats.["type"].ToObject<string>() |> CultureInfo.InvariantCulture.TextInfo.ToTitleCase
    let subtype = stats.["subtype"].ToObject<string>() |> CultureInfo.InvariantCulture.TextInfo.ToTitleCase
    let ac = stats.["armor_class"].ToObject<int>()
    let hp = stats.["hit_points"].ToObject<int>()
    let size = stats.["size"].ToObject<Size>()


    let level =
      match Int32.TryParse(stats.["challenge_rating"].ToObject<string>(), NumberStyles.Integer, CultureInfo.InvariantCulture) with
      | true, v  -> v
      | false, _ -> 1

    let prof = (level + 3) / 4 + 1

    let speeds =
      stats.["speed"].ToObject<JObject>().Properties()
      |> Seq.map (fun it -> Speed.ofString it.Path, it.Value.ToObject<int<ft/rnd>>())
      |> EnumMap

................................................................................
        | _ ->
          ()
              
        yield Skill.StrengthAttack, prof
        yield Skill.DexterityAttack, prof
      }
      |> EnumMap
      
    let casterLevel =
      match stats.TryGetValue("special_abilities") with
      | true, skills when skills.Type = JTokenType.Array ->
        seq {
          for it in skills.ToObject<JObject[]>() do
            let m = SpellcasterPattern.Match(it.["desc"].ToObject<string>())
            if m.Success then
              match Int32.TryParse(m.Groups.[1].Value, NumberStyles.Integer, CultureInfo.InvariantCulture) with
              | true, level -> yield level
              | false, _    -> ()
        }
        |> Seq.fold max 0
      | _ ->
        0
      
    let senses =
      (
        match stats.TryGetValue("senses") with
        | true, it when it.Type <> JTokenType.Null ->
          it.ToObject<string>()
          |> CommaPattern.Split
................................................................................
    
    {
      Name = name
      Race = if not (String.IsNullOrEmpty subtype) then sprintf "%s (%s)" typ subtype else typ
      Profession = String.Empty
      ArmorClass = ac
      MaxHitPoints = hp
      MaxSlots = Slot.ofLevel casterLevel
      Size = size
      Speeds = speeds
      Abilities = abilities
      Defenses = defenses
      Skills = skills
      Senses = senses
      Languages = languages
      TotalLevel = level
      CasterLevel = casterLevel
    }
    
  static let cache = LRUCache<string, StatBlock>(1024)

  let mutable slug = "commoner"
  let mutable stats : Option<StatBlock> = None

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *)

namespace Murphy.DragonDice
open System
open Murphy.DragonDice

/// Character class tags.
type Profession =
  | Alchemist = 0
  | Barbarian = 1
  | Bard = 2
  | Cleric = 3

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *)

namespace Murphy.DragonDice
open System


/// Character class tags.
type Profession =
  | Alchemist = 0
  | Barbarian = 1
  | Bard = 2
  | Cleric = 3

(*
 * Copyright (c) 2019-2020 by Thomas C. Chust <chust@web.de>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *)

namespace Murphy.DragonDice
open System

/// Spell slot tags.
type Slot =
  | Level1 = 1
  | Level2 = 2
  | Level3 = 3
  | Level4 = 4
  | Level5 = 5
  | Level6 = 6
  | Level7 = 7
  | Level8 = 8
  | Level9 = 9

/// Companion module for the spell slot type.
[<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
module Slot =
  /// Map a spell slot tag to a positive slot symbol
  let positiveSymbol (slot:Slot) =
    0x2460 + int slot - 1
    |> char
    
  /// Map a spell slot tag to a negative slot symbol
  let negativeSymbol (slot:Slot) =
    0x2776 + int slot - 1
    |> char
    
  /// Format total and used spell slots into a summary string.
  let toSummary (total:EnumMap<Slot, int>) (current:EnumMap<Slot, int>) =
    let buffer = Text.StringBuilder(32)
    for KeyValue (slot, n) in total do
      if n > 0 then
        if buffer.Length > 0 then buffer.Append(' ') |> ignore
        let u = current.[slot]
        for i = 0 to n-1 do
          buffer.Append(if i < u then positiveSymbol slot else negativeSymbol slot) |> ignore
    buffer.ToString()
    
  /// Get standard spell slots for total spellcaster level.
  let ofLevel level =
    seq {
      if   level >=  3 then yield Slot.Level1, 4
      elif level >=  2 then yield Slot.Level1, 3
      elif level >=  1 then yield Slot.Level1, 2
      
      if   level >=  4 then yield Slot.Level2, 3
      elif level >=  3 then yield Slot.Level2, 2
      
      if   level >=  6 then yield Slot.Level3, 3
      elif level >=  5 then yield Slot.Level3, 2
      
      if   level >=  9 then yield Slot.Level4, 3
      elif level >=  8 then yield Slot.Level4, 2
      elif level >=  7 then yield Slot.Level4, 1
      
      if   level >= 18 then yield Slot.Level5, 3
      elif level >= 10 then yield Slot.Level5, 2
      elif level >=  9 then yield Slot.Level5, 1
      
      if   level >= 19 then yield Slot.Level6, 2
      elif level >= 11 then yield Slot.Level6, 1
      
      if   level >= 20 then yield Slot.Level7, 2
      elif level >= 13 then yield Slot.Level7, 1

      if   level >= 15 then yield Slot.Level8, 1

      if   level >= 17 then yield Slot.Level9, 1
    }
    |> EnumMap

  /// Map a spell slot tag to a name.
  let inline toString (slot:Slot) =
    string (int slot)
    
  /// Try to map a spell slot name or symbol to a tag.
  let tryParse (s:string) =
    match s.ToLowerInvariant() with
    | "①" | "❶" | "1" -> Some Slot.Level1
    | "②" | "❷" | "2" -> Some Slot.Level2
    | "③" | "❸" | "3" -> Some Slot.Level3
    | "④" | "❹" | "4" -> Some Slot.Level4
    | "⑤" | "❺" | "5" -> Some Slot.Level5
    | "⑥" | "❻" | "6" -> Some Slot.Level6
    | "⑦" | "❼" | "7" -> Some Slot.Level7
    | "⑧" | "❽" | "8" -> Some Slot.Level8
    | "⑨" | "❾" | "9" -> Some Slot.Level9
    | _ ->
      None

  /// Map a spell slot name to a tag.
  let ofString s =
    match tryParse s with
    | Some slot -> slot
    | None      -> raise (FormatException "Invalid spell slot tag")

    /// Description of the character's profession.
    /// May contain character classes and levels.
    Profession : string
    /// Difficulty class of attacks against the character.
    ArmorClass : int
    /// Natural hit point maximum of the character.
    MaxHitPoints : int


    /// Physical size of the character.
    Size : Size
    /// Movements speeds of the character.
    Speeds : EnumMap<Speed, int<ft/rnd>>
    /// Ability scores of the character.
    Abilities : EnumMap<Ability, int>
    /// Damage immunities, resistances, or vulnerabilities of the character.
................................................................................
    /// Modifiers for saving throws and skill checks, including proficiency bonus but excluding ability modifiers.
    Skills : EnumMap<Skill, int>
    /// Detection ranges for the character's senses.
    Senses : EnumMap<Sense, int<ft>>
    /// Languages the character knows.
    Languages : Set<Language>
    /// Total character level.
    Level : int


  }
  
  /// The proficiency bonus derived from the total character level.
  member this.ProficiencyBonus =
    (this.Level + 3) / 4 + 1
  
  /// Compute the combined proficiency and ability modifier for a given skill.
  member this.GetModifier(skill:Skill) =
    this.Skills.[skill] + Ability.modifier this.Abilities.[Skill.ability skill]
  
/// Interface for character stats builders.
type IStatLayer =
................................................................................
  let Empty =
    {
      Name = String.Empty
      Race = String.Empty
      Profession = String.Empty
      ArmorClass = 0
      MaxHitPoints = 0

      Size = Size.Medium
      Speeds = EnumMap()
      Abilities = EnumMap()
      Defenses = List.empty
      Skills = EnumMap()
      Senses = EnumMap()
      Languages = Set.empty
      Level = 0

    }
    
  /// Build character stats from a list of layers.
  let build (layers:seq<#IStatLayer>) =
    layers
    |> Seq.fold (fun stats layer -> layer.Apply(stats)) Empty

    /// Description of the character's profession.
    /// May contain character classes and levels.
    Profession : string
    /// Difficulty class of attacks against the character.
    ArmorClass : int
    /// Natural hit point maximum of the character.
    MaxHitPoints : int
    /// Total spell slots of the character.
    MaxSlots : EnumMap<Slot, int>
    /// Physical size of the character.
    Size : Size
    /// Movements speeds of the character.
    Speeds : EnumMap<Speed, int<ft/rnd>>
    /// Ability scores of the character.
    Abilities : EnumMap<Ability, int>
    /// Damage immunities, resistances, or vulnerabilities of the character.
................................................................................
    /// Modifiers for saving throws and skill checks, including proficiency bonus but excluding ability modifiers.
    Skills : EnumMap<Skill, int>
    /// Detection ranges for the character's senses.
    Senses : EnumMap<Sense, int<ft>>
    /// Languages the character knows.
    Languages : Set<Language>
    /// Total character level.
    TotalLevel : int
    /// Spellcaster level of the character.
    CasterLevel : int
  }
  
  /// The proficiency bonus derived from the total character level.
  member this.ProficiencyBonus =
    (this.TotalLevel + 3) / 4 + 1
  
  /// Compute the combined proficiency and ability modifier for a given skill.
  member this.GetModifier(skill:Skill) =
    this.Skills.[skill] + Ability.modifier this.Abilities.[Skill.ability skill]
  
/// Interface for character stats builders.
type IStatLayer =
................................................................................
  let Empty =
    {
      Name = String.Empty
      Race = String.Empty
      Profession = String.Empty
      ArmorClass = 0
      MaxHitPoints = 0
      MaxSlots = EnumMap()
      Size = Size.Medium
      Speeds = EnumMap()
      Abilities = EnumMap()
      Defenses = List.empty
      Skills = EnumMap()
      Senses = EnumMap()
      Languages = Set.empty
      TotalLevel = 0
      CasterLevel = 0
    }
    
  /// Build character stats from a list of layers.
  let build (layers:seq<#IStatLayer>) =
    layers
    |> Seq.fold (fun stats layer -> layer.Apply(stats)) Empty