package level

import (
	"encoding/json"
	"fmt"
	"image"
	"math"

	"git.kirsle.net/apps/doodle/pkg/balance"
	"git.kirsle.net/apps/doodle/pkg/log"
	"git.kirsle.net/apps/doodle/pkg/pattern"
	"git.kirsle.net/apps/doodle/pkg/shmem"
	"git.kirsle.net/go/render"
	"github.com/google/uuid"
)

// Types of chunks.
const (
	MapType int = iota
	GridType
)

// Chunk holds a single portion of the pixel canvas.
type Chunk struct {
	Type int // map vs. 2D array.
	Accessor

	// Values told to it from higher up, not stored in JSON.
	Point render.Point
	Size  int

	// Texture cache properties so we don't redraw pixel-by-pixel every frame.
	uuid               uuid.UUID
	bitmap             image.Image
	texture            render.Texturer
	textureMasked      render.Texturer
	textureMaskedColor render.Color
	dirty              bool
}

// JSONChunk holds a lightweight (interface-free) copy of the Chunk for
// unmarshalling JSON files from disk.
type JSONChunk struct {
	Type    int             `json:"type"`
	Data    json.RawMessage `json:"data"`
	BinData interface{}     `json:"-"`
}

// Accessor provides a high-level API to interact with absolute pixel coordinates
// while abstracting away the details of how they're stored.
type Accessor interface {
	Inflate(*Palette) error
	Iter() <-chan Pixel
	IterViewport(viewport render.Rect) <-chan Pixel
	Get(render.Point) (*Swatch, error)
	Set(render.Point, *Swatch) error
	Delete(render.Point) error
	Len() int
	MarshalJSON() ([]byte, error)
	UnmarshalJSON([]byte) error
}

// NewChunk creates a new chunk.
func NewChunk() *Chunk {
	return &Chunk{
		Type:     MapType,
		Accessor: NewMapAccessor(),
	}
}

// Texture will return a cached texture for the rendering engine for this
// chunk's pixel data. If the cache is dirty it will be rebuilt in this func.
//
// Texture cache can be disabled with balance.DisableChunkTextureCache=true.
func (c *Chunk) Texture(e render.Engine) render.Texturer {
	if c.texture == nil || c.dirty {
		// Generate the normal bitmap and one with a color mask if applicable.
		tex, err := c.generateTexture(render.Invisible)
		if err != nil {
			log.Error("Texture: %s", err)
		}

		c.texture = tex
		c.textureMasked = nil // invalidate until next call
		c.dirty = false
	}
	return c.texture
}

// TextureMasked returns a cached texture with the ColorMask applied.
func (c *Chunk) TextureMasked(e render.Engine, mask render.Color) render.Texturer {
	if c.textureMasked == nil || c.textureMaskedColor != mask {
		// Force regenerate with the new mask color.
		c.dirty = true
		tex, err := c.generateTexture(mask)
		if err != nil {
			log.Error("Texture: %s", err)
		}

		c.textureMasked = tex
		c.textureMaskedColor = mask
	}
	return c.textureMasked
}

// SetDirty sets the `dirty` flag to true and forces the texture to be
// re-computed next frame.
func (c *Chunk) SetDirty() {
	c.dirty = true
}

// CachedBitmap returns a cached render of the chunk as a bitmap image.
//
// This is like Texture() but skips the step of actually producing an
// (SDL2) texture. The benefit of this is that you can call it from
// your non-main threads and offload the bitmap work into background
// tasks, then when SDL2 needs the Texture, the cached bitmap is
// immediately there saving time on the main thread.
func (c *Chunk) CachedBitmap(mask render.Color) image.Image {
	if c.bitmap == nil || c.dirty {
		c.bitmap = c.ToBitmap(mask)
	}
	return c.bitmap
}

// generateTexture takes the chunk's Bitmap, turns it into an (SDL2)
// texture, and caches the texture in memory until the chunk is marked
// as dirty.
func (c *Chunk) generateTexture(mask render.Color) (render.Texturer, error) {
	// Generate a unique name for this chunk cache.
	var name string
	if c.uuid == uuid.Nil {
		c.uuid = uuid.Must(uuid.NewUUID())
	}
	name = c.uuid.String()

	if mask != render.Invisible {
		name += fmt.Sprintf("-%02x%02x%02x%02x",
			mask.Red, mask.Green, mask.Blue, mask.Alpha,
		)
	}

	// Get (and/or cache) the chunk to a bitmap image.
	// Note: the 1st call to Bitmap or after SetDirty will
	// generate the image and store it cached.
	bitmap := c.CachedBitmap(mask)

	// Cache the texture data with the current renderer.
	tex, err := shmem.CurrentRenderEngine.StoreTexture(name, bitmap)
	return tex, err
}

// ToBitmap exports the chunk's pixels as a bitmap image.
// NOT CACHED! This will always run the logic. Use Bitmap() if you
// want a cached bitmap image that only generates itself once, and
// again when marked dirty.
func (c *Chunk) ToBitmap(mask render.Color) image.Image {
	canvas := c.SizePositive()
	imgSize := image.Rectangle{
		Min: image.Point{},
		Max: image.Point{
			X: c.Size,
			Y: c.Size,
		},
	}

	if imgSize.Max.X == 0 {
		imgSize.Max.X = int(canvas.W)
	}
	if imgSize.Max.Y == 0 {
		imgSize.Max.Y = int(canvas.H)
	}

	img := image.NewRGBA(imgSize)

	// Blank out the pixels.
	// TODO PERF: may be slow?
	for x := 0; x < img.Bounds().Max.X; x++ {
		for y := 0; y < img.Bounds().Max.Y; y++ {
			img.Set(x, y, balance.DebugChunkBitmapBackground.ToColor())
		}
	}

	// Pixel coordinate offset to map the Chunk World Position to the
	// smaller image boundaries.
	pointOffset := render.Point{
		X: c.Point.X * c.Size,
		Y: c.Point.Y * c.Size,
	}

	// Blot all the pixels onto it.
	for px := range c.Iter() {
		var color = px.Swatch.Color

		// If the swatch has a pattern, mesh it in.
		if px.Swatch.Pattern != "" {
			color = pattern.SampleColor(px.Swatch.Pattern, color, px.Point())
		}

		if mask != render.Invisible {
			// A semi-transparent mask will overlay on top of the actual color.
			if mask.Alpha < 255 {
				color = color.AddColor(mask)
			} else {
				color = mask
			}
		}
		img.Set(
			px.X-pointOffset.X,
			px.Y-pointOffset.Y,
			color.ToColor(),
		)
	}

	return img
}

// Teardown the chunk and free (SDL2) texture memory in ways Go can not by itself.
// Returns the number of textures freed.
func (c *Chunk) Teardown() int {
	var freed int

	if c.texture != nil {
		c.texture.Free()
		c.texture = nil
		freed++
	}

	if c.textureMasked != nil {
		c.textureMasked.Free()
		c.textureMasked = nil
		freed++
	}

	return freed
}

// Set proxies to the accessor and flags the texture as dirty.
func (c *Chunk) Set(p render.Point, sw *Swatch) error {
	c.dirty = true
	return c.Accessor.Set(p, sw)
}

// Delete proxies to the accessor and flags the texture as dirty.
func (c *Chunk) Delete(p render.Point) error {
	c.dirty = true
	return c.Accessor.Delete(p)
}

// Rect returns the bounding coordinates that the Chunk has pixels for.
func (c *Chunk) Rect() render.Rect {
	// Lowest and highest chunks.
	var (
		lowest  render.Point
		highest render.Point
	)

	for coord := range c.Iter() {
		if coord.X < lowest.X {
			lowest.X = coord.X
		}
		if coord.Y < lowest.Y {
			lowest.Y = coord.Y
		}

		if coord.X > highest.X {
			highest.X = coord.X
		}
		if coord.Y > highest.Y {
			highest.Y = coord.Y
		}
	}

	return render.Rect{
		X: lowest.X,
		Y: lowest.Y,
		W: highest.X,
		H: highest.Y,
	}
}

// SizePositive returns the Size anchored to 0,0 with only positive
// coordinates.
func (c *Chunk) SizePositive() render.Rect {
	S := c.Rect()
	return render.Rect{
		W: int(math.Abs(float64(S.X))) + S.W,
		H: int(math.Abs(float64(S.Y))) + S.H,
	}
}

// Usage returns the percent of free space vs. allocated pixels in the chunk.
func (c *Chunk) Usage(size int) float64 {
	return float64(c.Len()) / float64(size)
}

// MarshalJSON writes the chunk to JSON.
func (c *Chunk) MarshalJSON() ([]byte, error) {
	data, err := c.Accessor.MarshalJSON()
	if err != nil {
		return []byte{}, err
	}

	generic := &JSONChunk{
		Type: c.Type,
		Data: data,
	}
	b, err := json.Marshal(generic)
	return b, err
}

// UnmarshalJSON loads the chunk from JSON and uses the correct accessor to
// parse the inner details.
func (c *Chunk) UnmarshalJSON(b []byte) error {
	// Parse it generically so we can hand off the inner "data" object to the
	// right accessor for unmarshalling.
	generic := &JSONChunk{}
	err := json.Unmarshal(b, generic)
	if err != nil {
		return fmt.Errorf("Chunk.UnmarshalJSON: failed to unmarshal into generic JSONChunk type: %s", err)
	}

	switch c.Type {
	case MapType:
		c.Accessor = NewMapAccessor()
		return c.Accessor.UnmarshalJSON(generic.Data)
	default:
		return fmt.Errorf("Chunk.UnmarshalJSON: unsupported chunk type '%d'", c.Type)
	}
}