package app

import (
	"fmt"
	"image"
	"os"
	"strconv"
	"strings"
	"sync"

	"git.sr.ht/~rockorager/vaxis"
	"git.sr.ht/~rjarry/aerc/lib/log"
	"git.sr.ht/~rjarry/aerc/lib/parse"
	"git.sr.ht/~rjarry/aerc/lib/ui"

	_ "image/jpeg"
	_ "image/png"

	_ "golang.org/x/image/bmp"
	_ "golang.org/x/image/tiff"
	_ "golang.org/x/image/webp"
)

const (
	blockText  = 0
	blockImage = 1

	defaultImageHeight = 15
)

type contentBlock struct {
	blockType int
	lines     []string
	imageIdx  int
}

type compositeContent struct {
	blocks []contentBlock
	images []parse.ImageRef
	width  int

	mu       sync.Mutex
	decoded  map[int]image.Image
	decErrs  map[int]bool // true = decode attempted and failed
	graphics map[int]vaxis.Image

	invalidate func() // callback to trigger redraw after async decode
}

func splitContentBlocks(text string, images []parse.ImageRef) []contentBlock {
	imageSet := make(map[int]bool, len(images))
	for _, img := range images {
		imageSet[img.Index] = true
	}

	var blocks []contentBlock
	var currentLines []string

	lines := strings.Split(text, "\n")
	if len(lines) > 0 && lines[len(lines)-1] == "" {
		lines = lines[:len(lines)-1]
	}

	for _, line := range lines {
		if idx, ok := parsePlaceholder(line); ok && imageSet[idx] {
			if len(currentLines) > 0 {
				blocks = append(blocks, contentBlock{
					blockType: blockText,
					lines:     currentLines,
				})
				currentLines = nil
			}
			blocks = append(blocks, contentBlock{
				blockType: blockImage,
				imageIdx:  idx,
			})
		} else {
			currentLines = append(currentLines, line)
		}
	}
	if len(currentLines) > 0 {
		blocks = append(blocks, contentBlock{
			blockType: blockText,
			lines:     currentLines,
		})
	}
	return blocks
}

func parsePlaceholder(line string) (int, bool) {
	if !strings.HasPrefix(line, "\x00IMG:") || !strings.HasSuffix(line, "\x00") {
		return 0, false
	}
	numStr := line[len("\x00IMG:") : len(line)-1]
	idx, err := strconv.Atoi(numStr)
	if err != nil {
		return 0, false
	}
	return idx, true
}

func newCompositeContent(text string, images []parse.ImageRef, width int, invalidate func()) *compositeContent {
	cc := &compositeContent{
		blocks:     splitContentBlocks(text, images),
		images:     images,
		width:      width,
		decoded:    make(map[int]image.Image),
		decErrs:    make(map[int]bool),
		graphics:   make(map[int]vaxis.Image),
		invalidate: invalidate,
	}
	// Decode all images in background
	go cc.decodeAllImages()
	return cc
}

// decodeAllImages decodes all referenced images in a background goroutine.
// Calls invalidate() when done so the UI redraws with images.
func (cc *compositeContent) decodeAllImages() {
	defer log.PanicHandler()
	for i, img := range cc.images {
		f, err := os.Open(img.Path)
		if err != nil {
			log.Debugf("composite: open image %d: %v", i, err)
			cc.mu.Lock()
			cc.decErrs[i] = true
			cc.mu.Unlock()
			continue
		}
		decoded, _, err := image.Decode(f)
		f.Close()
		if err != nil {
			log.Debugf("composite: decode image %d: %v", i, err)
			cc.mu.Lock()
			cc.decErrs[i] = true
			cc.mu.Unlock()
			continue
		}
		cc.mu.Lock()
		cc.decoded[i] = decoded
		cc.mu.Unlock()
	}
	if cc.invalidate != nil {
		cc.invalidate()
	}
}

func (cc *compositeContent) totalHeight() int {
	h := 0
	for _, b := range cc.blocks {
		switch b.blockType {
		case blockText:
			h += len(b.lines)
		case blockImage:
			h += cc.imageHeight(b.imageIdx)
		}
	}
	return h
}

func (cc *compositeContent) imageHeight(idx int) int {
	cc.mu.Lock()
	img, ok := cc.decoded[idx]
	cc.mu.Unlock()
	if ok {
		bounds := img.Bounds()
		if bounds.Dx() == 0 {
			return defaultImageHeight
		}
		ratio := float64(bounds.Dy()) / float64(bounds.Dx())
		h := int(float64(cc.width) * ratio / 2.0)
		if h < 3 {
			h = 3
		}
		if h > defaultImageHeight {
			h = defaultImageHeight
		}
		return h
	}
	return defaultImageHeight
}

func (cc *compositeContent) Destroy() {
	cc.mu.Lock()
	defer cc.mu.Unlock()
	for _, g := range cc.graphics {
		g.Destroy()
	}
	cc.graphics = make(map[int]vaxis.Image)
}

func (cc *compositeContent) CleanupFiles() {
	for _, img := range cc.images {
		os.Remove(img.Path)
	}
}

// Draw renders composite content. Only renders images that are already decoded.
func (cc *compositeContent) Draw(ctx *ui.Context, scroll int, style ...vaxis.Style) {
	width := ctx.Width()
	height := ctx.Height()
	row := -scroll

	defaultStyle := vaxis.Style{}
	if len(style) > 0 {
		defaultStyle = style[0]
	}

	for _, b := range cc.blocks {
		switch b.blockType {
		case blockText:
			for _, line := range b.lines {
				if row >= height {
					return
				}
				if row >= 0 {
					ctx.Printf(0, row, defaultStyle, "%s",
						truncateLine(line, width))
				}
				row++
			}
		case blockImage:
			imgH := cc.imageHeight(b.imageIdx)
			if row+imgH > 0 && row < height {
				cc.drawImage(ctx, b.imageIdx, row, width, imgH, defaultStyle)
			}
			row += imgH
		}
	}
}

func (cc *compositeContent) drawImage(ctx *ui.Context, idx, row, width, height int, style vaxis.Style) {
	cc.mu.Lock()
	img, decoded := cc.decoded[idx]
	failed := cc.decErrs[idx]
	cc.mu.Unlock()

	// Show alt text if not yet decoded or failed
	if !decoded {
		alt := "[loading image...]"
		if failed {
			alt = "[image]"
			if idx < len(cc.images) && cc.images[idx].Alt != "" {
				alt = fmt.Sprintf("[%s]", cc.images[idx].Alt)
			}
		}
		if row >= 0 && row < ctx.Height() {
			ctx.Printf(0, row, style, "%s", alt)
		}
		return
	}

	vx := ctx.Window().Vx
	graphic, ok := cc.graphics[idx]
	if !ok {
		var err error
		graphic, err = vx.NewImage(img)
		if err != nil {
			log.Errorf("composite: vaxis NewImage %d: %v", idx, err)
			if row >= 0 && row < ctx.Height() {
				alt := "[image: render error]"
				if idx < len(cc.images) && cc.images[idx].Alt != "" {
					alt = fmt.Sprintf("[%s]", cc.images[idx].Alt)
				}
				ctx.Printf(0, row, style, "%s", alt)
			}
			return
		}
		cc.graphics[idx] = graphic
	}

	graphic.Resize(width, height)

	startRow := row
	if startRow < 0 {
		startRow = 0
	}
	win := ctx.Window().New(0, startRow, width, height)
	graphic.Draw(win)
}

func truncateLine(s string, width int) string {
	runes := []rune(s)
	if len(runes) <= width {
		return s
	}
	return string(runes[:width])
}