package uix

import (
	"fmt"
	"os"
	"strings"

	"git.kirsle.net/apps/doodle/lib/events"
	"git.kirsle.net/apps/doodle/lib/render"
	"git.kirsle.net/apps/doodle/lib/ui"
	"git.kirsle.net/apps/doodle/pkg/balance"
	"git.kirsle.net/apps/doodle/pkg/collision"
	"git.kirsle.net/apps/doodle/pkg/doodads"
	"git.kirsle.net/apps/doodle/pkg/level"
	"git.kirsle.net/apps/doodle/pkg/log"
	"git.kirsle.net/apps/doodle/pkg/scripting"
	"git.kirsle.net/apps/doodle/pkg/wallpaper"
)

// Canvas is a custom ui.Widget that manages a single drawing.
type Canvas struct {
	ui.Frame
	Palette *level.Palette

	// Editable and Scrollable go hand in hand and, if you initialize a
	// NewCanvas() with editable=true, they are both enabled.
	Editable   bool // Clicking will edit pixels of this canvas.
	Scrollable bool // Cursor keys will scroll the viewport of this canvas.

	// Selected draw tool/mode, default Pencil, for editable canvases.
	Tool Tool

	// MaskColor will force every pixel to render as this color regardless of
	// the palette index of that pixel. Otherwise pixels behave the same and
	// the palette does work as normal. Set to render.Invisible (zero value)
	// to remove the mask.
	MaskColor render.Color

	// Actor ID to follow the camera on automatically, i.e. the main player.
	FollowActor string

	// Debug tools
	// NoLimitScroll suppresses the scroll limit for bounded levels.
	NoLimitScroll bool

	// Underlying chunk data for the drawing.
	chunks *level.Chunker

	// Actors to superimpose on top of the drawing.
	actor  *Actor   // if this canvas IS an actor
	actors []*Actor // if this canvas CONTAINS actors (i.e., is a level)

	// Doodad scripting engine supervisor.
	// NOTE: initialized and managed by the play_scene.
	scripting *scripting.Supervisor

	// Wallpaper settings.
	wallpaper *Wallpaper

	// When the Canvas wants to delete Actors, but ultimately it is upstream
	// that controls the actors. Upstream should delete them and then reinstall
	// the actor list from scratch.
	OnDeleteActors func([]*level.Actor)
	OnDragStart    func(filename string)

	// Tracking pixels while editing. TODO: get rid of pixelHistory?
	pixelHistory []*level.Pixel
	lastPixel    *level.Pixel

	// We inherit the ui.Widget which manages the width and height.
	Scroll render.Point // Scroll offset for which parts of canvas are visible.
}

// NewCanvas initializes a Canvas widget.
//
// If editable is true, Scrollable is also set to true, which means the arrow
// keys will scroll the canvas viewport which is desirable in Edit Mode.
func NewCanvas(size int, editable bool) *Canvas {
	w := &Canvas{
		Editable:   editable,
		Scrollable: editable,
		Palette:    level.NewPalette(),
		chunks:     level.NewChunker(size),
		actors:     make([]*Actor, 0),
		wallpaper:  &Wallpaper{},
	}
	w.setup()
	w.IDFunc(func() string {
		var attrs []string

		if w.Editable {
			attrs = append(attrs, "editable")
		} else {
			attrs = append(attrs, "read-only")
		}

		if w.Scrollable {
			attrs = append(attrs, "scrollable")
		}

		return fmt.Sprintf("Canvas<%d; %s>", size, strings.Join(attrs, "; "))
	})
	return w
}

// Load initializes the Canvas using an existing Palette and Grid.
func (w *Canvas) Load(p *level.Palette, g *level.Chunker) {
	w.Palette = p
	w.chunks = g

	if len(w.Palette.Swatches) > 0 {
		w.SetSwatch(w.Palette.Swatches[0])
	}
}

// LoadLevel initializes a Canvas from a Level object.
func (w *Canvas) LoadLevel(e render.Engine, level *level.Level) {
	w.Load(level.Palette, level.Chunker)

	// TODO: wallpaper paths
	filename := "assets/wallpapers/" + level.Wallpaper
	if _, err := os.Stat(filename); os.IsNotExist(err) {
		log.Error("LoadLevel: %s", err)
		filename = "assets/wallpapers/notebook.png" // XXX TODO
	}

	wp, err := wallpaper.FromFile(e, filename)
	if err != nil {
		log.Error("wallpaper FromFile(%s): %s", filename, err)
	}

	w.wallpaper.maxWidth = level.MaxWidth
	w.wallpaper.maxHeight = level.MaxHeight
	err = w.wallpaper.Load(e, level.PageType, wp)
	if err != nil {
		log.Error("wallpaper Load: %s", err)
	}
}

// LoadDoodad initializes a Canvas from a Doodad object.
func (w *Canvas) LoadDoodad(d *doodads.Doodad) {
	// TODO more safe
	w.Load(d.Palette, d.Layers[0].Chunker)
}

// SetSwatch changes the currently selected swatch for editing.
func (w *Canvas) SetSwatch(s *level.Swatch) {
	w.Palette.ActiveSwatch = s
}

// setup common configs between both initializers of the canvas.
func (w *Canvas) setup() {
	// XXX: Debug code.
	if balance.DebugCanvasBorder != render.Invisible {
		w.Configure(ui.Config{
			BorderColor: balance.DebugCanvasBorder,
			BorderSize:  2,
			BorderStyle: ui.BorderSolid,
		})
	}
}

// Loop is called on the scene's event loop to handle mouse interaction with
// the canvas, i.e. to edit it.
func (w *Canvas) Loop(ev *events.State) error {
	// Process the arrow keys scrolling the level in Edit Mode.
	// canvas_scrolling.go
	w.loopEditorScroll(ev)
	if err := w.loopFollowActor(ev); err != nil {
		log.Error("Follow actor: %s", err) // not fatal but nice to know
	}
	_ = w.loopConstrainScroll()

	// Remove any actors that were destroyed the previous tick.
	var newActors []*Actor
	for _, a := range w.actors {
		if a.flagDestroy {
			continue
		}
		newActors = append(newActors, a)
	}
	if len(newActors) < len(w.actors) {
		w.actors = newActors
	}

	// Move any actors. As we iterate over all actors, track their bounding
	// rectangles so we can later see if any pair of actors intersect each other.
	boxes := make([]render.Rect, len(w.actors))
	for i, a := range w.actors {
		// Get the actor's velocity to see if it's moving this tick.
		v := a.Velocity()

		// If not moving, grab the bounding box right now.
		if v == render.Origin {
			boxes[i] = doodads.GetBoundingRect(a)
			continue
		}

		// Create a delta point from their current location to where they
		// want to move to this tick.
		delta := a.Position()
		delta.Add(v)

		// Check collision with level geometry.
		info, ok := collision.CollidesWithGrid(a, w.chunks, delta)
		if ok {
			// Collision happened with world.
		}
		delta = info.MoveTo // Move us back where the collision check put us

		// Move the actor's World Position to the new location.
		a.MoveTo(delta)

		// Keep the actor from leaving the world borders of bounded maps.
		w.loopContainActorsInsideLevel(a)

		// Store this actor's bounding box after they've moved.
		boxes[i] = doodads.GetBoundingRect(a)
	}

	// Check collisions between actors.
	for tuple := range collision.BetweenBoxes(boxes) {
		log.Debug("Actor %s collides with %s",
			w.actors[tuple[0]].ID(),
			w.actors[tuple[1]].ID(),
		)
		a, b := w.actors[tuple[0]], w.actors[tuple[1]]

		// Call the OnCollide handler.
		if w.scripting != nil {
			if err := w.scripting.To(a.ID()).Events.RunCollide(); err != nil {
				log.Error(err.Error())
			}
			if err := w.scripting.To(b.ID()).Events.RunCollide(); err != nil {
				log.Error(err.Error())
			}
		}
	}

	// If the canvas is editable, only care if it's over our space.
	if w.Editable {
		cursor := render.NewPoint(ev.CursorX.Now, ev.CursorY.Now)
		if cursor.Inside(ui.AbsoluteRect(w)) {
			return w.loopEditable(ev)
		}
	}
	return nil
}

// Viewport returns a rect containing the viewable drawing coordinates in this
// canvas. The X,Y values are the scroll offset (top left) and the W,H values
// are the scroll offset plus the width/height of the Canvas widget.
//
// The Viewport rect are the Absolute World Coordinates of the drawing that are
// visible inside the Canvas. The X,Y is the top left World Coordinate and the
// W,H are the bottom right World Coordinate, making this rect an absolute
// slice of the world. For a normal rect with a relative width and height,
// use ViewportRelative().
//
// The rect X,Y are the negative Scroll Value.
// The rect W,H are the Canvas widget size minus the Scroll Value.
func (w *Canvas) Viewport() render.Rect {
	var S = w.Size()
	return render.Rect{
		X: -w.Scroll.X,
		Y: -w.Scroll.Y,
		W: S.W - w.Scroll.X,
		H: S.H - w.Scroll.Y,
	}
}

// ViewportRelative returns a relative viewport where the Width and Height
// values are zero-relative: so you can use it with point.Inside(viewport)
// to see if a World Index point should be visible on screen.
//
// The rect X,Y are the negative Scroll Value
// The rect W,H are the Canvas widget size.
func (w *Canvas) ViewportRelative() render.Rect {
	var S = w.Size()
	return render.Rect{
		X: -w.Scroll.X,
		Y: -w.Scroll.Y,
		W: S.W,
		H: S.H,
	}
}

// WorldIndexAt returns the World Index that corresponds to a Screen Pixel
// on the screen. If the screen pixel is the mouse coordinate (relative to
// the application window) this will return the World Index of the pixel below
// the mouse cursor.
func (w *Canvas) WorldIndexAt(screenPixel render.Point) render.Point {
	var P = ui.AbsolutePosition(w)
	return render.Point{
		X: screenPixel.X - P.X - w.Scroll.X,
		Y: screenPixel.Y - P.Y - w.Scroll.Y,
	}
}

// Chunker returns the underlying Chunker object.
func (w *Canvas) Chunker() *level.Chunker {
	return w.chunks
}

// ScrollTo sets the viewport scroll position.
func (w *Canvas) ScrollTo(to render.Point) {
	w.Scroll.X = to.X
	w.Scroll.Y = to.Y
}

// ScrollBy adjusts the viewport scroll position.
func (w *Canvas) ScrollBy(by render.Point) {
	w.Scroll.Add(by)
}

// Compute the canvas.
func (w *Canvas) Compute(e render.Engine) {

}