package uix

import (
	"fmt"
	"runtime"
	"strings"

	"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/drawtool"
	"git.kirsle.net/apps/doodle/pkg/filesystem"
	"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"
	"git.kirsle.net/go/render"
	"git.kirsle.net/go/render/event"
	"git.kirsle.net/go/ui"
)

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

	// Parent Canvas widget, e.g. for Actors inside of a Level so they can
	// find the parent canvas and see where they are drawing in relation to
	// it (to handle top/left edge cropping on scroll)
	parent *Canvas

	// 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.
	Zoom       int  // Zoom level on the canvas.

	// Custom label to place in the lower-right corner of the canvas.
	// Used for e.g. the quantity badge on Inventory items.
	CornerLabel string

	// Selected draw tool/mode, default Pencil, for editable canvases.
	Tool      drawtool.Tool
	BrushSize int // thickness of selected brush

	// 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.
	level    *level.Level
	chunks   *level.Chunker
	doodad   *doodads.Doodad
	modified bool // set to True when the drawing has been modified, like in Editor Mode.

	// 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)

	// Collision memory for the actors.
	collidingActors map[*Actor]*Actor // mapping their IDs to each other

	// 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([]*Actor)
	OnDragStart    func(*level.Actor)

	// -- WHEN Canvas.Tool is "Link" --
	// When the Canvas wants to link two actors together. Arguments are the IDs
	// of the two actors.
	OnLinkActors func(a, b *Actor)
	linkFirst    *Actor

	// Collision handlers for level geometry.
	OnLevelCollision func(*Actor, *collision.Collide)

	// Handler when a doodad script called Actors.SetPlayerCharacter.
	// The filename.doodad is given.
	OnSetPlayerCharacter func(filename string)

	// Handler for when a doodad script calls Level.ResetTimer().
	OnResetTimer func()

	/********
	 * Editable canvas private variables.
	 ********/
	// The current stroke actively being drawn by the user, during a
	// mousedown-and-dragging event.
	currentStroke *drawtool.Stroke
	strokes       map[int]*drawtool.Stroke // active stroke mapped by ID
	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.
	scrollDragging  bool         // Middle-click to pan scroll
	scrollStartAt   render.Point // Cursor point at beginning of pan
	scrollWasAt     render.Point // copy of Scroll at beginning of pan
	scrollLastDelta render.Point // multitouch spam

	// LoadUnloadChunks metrics for the debug overlay.
	loadUnloadInside  int
	loadUnloadOutside int
}

// 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(),
		BrushSize:  1,
		chunks:     level.NewChunker(size),
		actors:     make([]*Actor, 0),
		wallpaper:  &Wallpaper{},

		strokes: map[int]*drawtool.Stroke{},
	}
	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
}

/*
Destroy the canvas.

This function satisfies the ui.Widget interface but it also calls Teardown() methods
on the level or doodad as well as any level actors, which frees up SDL2 texture memory.

Note: the rest of the data can be garbage collected by Go normally, the textures are
able to regenerate themselves again if needed.
*/
func (w *Canvas) Destroy() {
	if w.level != nil {
		w.level.Teardown()
	}

	if w.doodad != nil {
		w.doodad.Teardown()
	}

	for _, actor := range w.actors {
		actor.Canvas.Destroy()
	}

	if w.wallpaper.WP != nil {
		if freed := w.wallpaper.WP.Free(); freed > 0 {
			log.Debug("%s.Destroy(): freed %d wallpaper textures", w, freed)
		}
	}

	if w.scripting != nil {
		w.scripting.Teardown()
	}
}

// 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
	w.modified = false

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

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

	// TODO: wallpaper paths
	filename := balance.EmbeddedWallpaperBasePath + level.Wallpaper
	if runtime.GOOS != "js" {
		// Check if the wallpaper wasn't found. Check bindata and file system.
		if _, err := filesystem.FindFileEmbedded(filename, level); err != nil {
			log.Error("LoadLevel: wallpaper %s did not appear to exist, default to notebook.png", filename)
			filename = balance.EmbeddedWallpaperBasePath + "notebook.png"
		}
	}

	wp, err := wallpaper.FromFile(filename, level)
	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(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.doodad = d
	w.Load(d.Palette, d.Layers[0].Chunker)
}

// LoadDoodadToLayer initializes a Canvas from a Doodad object and picks
// a layer to load.
func (w *Canvas) LoadDoodadToLayer(d *doodads.Doodad, index int) {
	if index < 0 || index > len(d.Layers) {
		log.Error("LoadDoodadToLayer: index %d out of range", index)
		return
	}
	w.Load(d.Palette, d.Layers[index].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 *event.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()

	// Every so often, eager-load/unload chunk bitmaps to save on memory.
	w.LoadUnloadChunks()

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

	// Check collisions between actors.
	if w.scripting != nil {
		if err := w.loopActorCollision(); err != nil {
			log.Error("loopActorCollision: %s", err)
		}
	}

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

// LoadingViewport is the viewport of chunks that ought to be preloaded and
// ready to display soon. It is the Viewport of chunks on screen + a margin
// of neighboring chunks outside the screen.
//
// For memory optimization, chunks falling inside this viewport have their
// Go image.Image rendered and cached ready to convert to an SDL2 Texture
// when they come on screen. Chunks outside of the LoadingViewport can be
// unloaded (textures and images freed) to keep memory consumption on large
// levels under control.
func (w *Canvas) LoadingViewport() render.Rect {
	var (
		chunkSize int
		vp        = w.Viewport()
		margin    = balance.LoadingViewportMarginChunks
	)

	// This function is meant for levels only, but..
	if w.level != nil {
		chunkSize = w.level.Chunker.Size
	} else if w.doodad != nil {
		chunkSize = w.doodad.ChunkSize()
	} else {
		chunkSize = balance.ChunkSize
		log.Error("Canvas.LoadingViewport: no drawing to get chunk size from, default to %d", chunkSize)
	}

	return render.Rect{
		X: vp.X - chunkSize*margin,
		Y: vp.Y - chunkSize*margin,
		W: vp.W + chunkSize*margin,
		H: vp.H + chunkSize*margin,
	}
}

// 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)
	world := render.Point{
		X: screenPixel.X - P.X - w.Scroll.X,
		Y: screenPixel.Y - P.Y - w.Scroll.Y,
	}

	// Handle Zoomies
	if w.Zoom != 0 {
		// Zoom Out - logic is 100% correct, do not touch.
		// ZoomDivide's logic at time of writing is to:
		//    return int(float64(v) * divider)
		// Where divider is a map of w.Zoom to:
		//    -2=4  -1=2  0=1  1=0.5  2=0.25  3=0.125
		// The -2 and -1 do the right things (zoom out), zoom
		// in was jank. NOW FIXED with the following maps:
		//    -2=4  -1=2  0=1  1=0.675  2=0.5  3=0.404
		// Values for zoom levels 1 and 3 are jank but works?
		world.X = w.ZoomDivide(world.X)
		world.Y = w.ZoomDivide(world.Y)
	}

	return world
}

// 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) {

}