module SketchToolbar = {
  @module("./SketchToolbar.jsx") @react.component
  external make: (
    ~state: UseSketch.sketchState,
    ~onSetTool: UseSketch.tool => unit,
    ~onSetColor: UseSketch.color => unit,
    ~onClear: unit => unit,
    ~onSave: unit => unit,
    ~onClose: unit => unit,
  ) => React.element = "default"
}

type point = {x: float, y: float}

@val external document: {..} = "document"
external asCanvas: Dom.element => {..} = "%identity"

@react.component
let make = (
  ~isActive: bool,
  ~tool: UseSketch.tool,
  ~color: UseSketch.color,
  ~onSave: unit => unit,
  ~onClear: unit => unit,
  ~onClose: unit => unit,
  ~onSetTool: UseSketch.tool => unit,
  ~onSetColor: UseSketch.color => unit,
) => {
  let canvasRef: React.ref<Nullable.t<Dom.element>> = React.useRef(Nullable.null)
  let isDrawing = React.useRef(false)
  let lastPoint = React.useRef(None)

  React.useEffect1(() => {
    switch canvasRef.current->Nullable.toOption {
    | None => ()
    | Some(el) =>
      let canvas = asCanvas(el)
      let parent = canvas["parentElement"]
      canvas["width"] = parent["offsetWidth"]
      canvas["height"] = parent["offsetHeight"]
    }
    None
  }, [isActive])

  let getPos = (e: JsxEvent.Mouse.t, canvas) => {
    let rect = canvas["getBoundingClientRect"]()
    {
      x: Float.fromInt(JsxEvent.Mouse.clientX(e)) -. rect["left"],
      y: Float.fromInt(JsxEvent.Mouse.clientY(e)) -. rect["top"],
    }
  }

  let startDraw = (e: JsxEvent.Mouse.t) => {
    switch canvasRef.current->Nullable.toOption {
    | None => ()
    | Some(el) =>
      let canvas = asCanvas(el)
      isDrawing.current = true
      let pos = getPos(e, canvas)
      lastPoint.current = Some(pos)
      if tool === UseSketch.Highlighter {
        let ctx = canvas["getContext"]("2d")
        let hex = UseSketch.colorToHex(color)
        let width = UseSketch.toolToWidth(tool, 2.0)
        ctx["globalAlpha"] = 0.25
        ctx["globalCompositeOperation"] = "source-over"
        ctx["strokeStyle"] = hex
        ctx["lineWidth"] = width
        ctx["lineCap"] = "round"
        ctx["lineJoin"] = "round"
        let _ = ctx["beginPath"]()
        let _ = ctx["moveTo"](pos.x, pos.y)
      } else if tool === UseSketch.Text {
        let text = canvas["ownerDocument"]["defaultView"]["prompt"]("Enter text:", "")
        switch Nullable.toOption(text) {
        | None => ()
        | Some(t) =>
          let ctx = canvas["getContext"]("2d")
          let hex = UseSketch.colorToHex(color)
          ctx["globalAlpha"] = 1.0
          ctx["fillStyle"] = hex
          ctx["font"] = "bold 16px sans-serif"
          let _ = ctx["fillText"](t, pos.x, pos.y)
        }
      }
    }
  }

  let draw = (e: JsxEvent.Mouse.t) => {
    if isDrawing.current && tool !== UseSketch.Text {
      switch canvasRef.current->Nullable.toOption {
      | None => ()
      | Some(el) =>
        let canvas = asCanvas(el)
        switch lastPoint.current {
        | None => ()
        | Some(last) =>
          let ctx = canvas["getContext"]("2d")
          let pos = getPos(e, canvas)
          let hex = UseSketch.colorToHex(color)
          let width = UseSketch.toolToWidth(tool, 2.0)
          switch tool {
          | UseSketch.Highlighter =>
            let _ = ctx["lineTo"](pos.x, pos.y)
            let _ = ctx["stroke"]()
          | _ =>
            ctx["globalAlpha"] = 1.0
            ctx["strokeStyle"] = hex
            ctx["lineWidth"] = width
            ctx["lineCap"] = "round"
            ctx["lineJoin"] = "round"
            let _ = ctx["beginPath"]()
            let _ = ctx["moveTo"](last.x, last.y)
            let _ = ctx["quadraticCurveTo"](
              last.x +. (pos.x -. last.x) /. 2.0,
              last.y +. (pos.y -. last.y) /. 2.0,
              pos.x,
              pos.y,
            )
            let _ = ctx["stroke"]()
          }
          lastPoint.current = Some(pos)
        }
      }
    }
  }

  let stopDraw = (_e: JsxEvent.Mouse.t) => {
    if tool === UseSketch.Highlighter {
      switch canvasRef.current->Nullable.toOption {
      | None => ()
      | Some(el) =>
        let canvas = asCanvas(el)
        let ctx = canvas["getContext"]("2d")
        let _ = ctx["stroke"]()
        ctx["globalAlpha"] = 1.0
        ctx["globalCompositeOperation"] = "source-over"
      }
    }
    isDrawing.current = false
    lastPoint.current = None
  }

  let handleClear = () => {
    switch canvasRef.current->Nullable.toOption {
    | None => ()
    | Some(el) =>
      let canvas = asCanvas(el)
      let ctx = canvas["getContext"]("2d")
      let _ = ctx["clearRect"](0, 0, canvas["width"], canvas["height"])
      onClear()
    }
  }

  let handleSave = () => {
    switch canvasRef.current->Nullable.toOption {
    | None => ()
    | Some(el) =>
      let canvas = asCanvas(el)
      let dataUrl = canvas["toDataURL"]("image/png")
      let link = document["createElement"]("a")
      link["href"] = dataUrl
      link["download"] = "sketch.png"
      let _ = link["click"]()
      onSave()
    }
  }

  if !isActive {
    React.null
  } else {
    <div className="absolute inset-0 z-10" style={{pointerEvents: isActive ? "all" : "none"}}>
      <SketchToolbar.make
        state={{
          UseSketch.isActive,
          tool,
          color,
          strokeWidth: 2.0,
        }}
        onSetTool={onSetTool}
        onSetColor={onSetColor}
        onClear={handleClear}
        onSave={handleSave}
        onClose={onClose}
      />
      <canvas
        ref={canvasRef->ReactDOM.Ref.domRef}
        width="100%"
        height="100%"
        className="w-full h-full cursor-crosshair"
        onMouseDown={startDraw}
        onMouseMove={draw}
        onMouseUp={stopDraw}
        onMouseLeave={stopDraw}
      />
    </div>
  }
}