package jobs

import (
	"bytes"
	"context"
	"html"
	"image"
	"image/color"
	"image/draw"
	_ "image/gif"
	"image/jpeg"
	_ "image/png"
	"io"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"time"

	"golang.org/x/image/font"
	"golang.org/x/image/font/basicfont"
	"golang.org/x/image/math/fixed"
	_ "golang.org/x/image/webp"
	"warpbox.dev/backend/libs/config"
	"warpbox.dev/backend/libs/services"
)

type ThumbnailJobResult struct {
	Scanned   int
	Generated int
	Failed    int
}

func GenerateThumbnailsForBoxAsync(uploadService *services.UploadService, logger *slog.Logger, boxID string) {
	go func() {
		box, err := uploadService.GetBox(boxID)
		if err != nil {
			logger.Warn("thumbnail box lookup failed", "source", "thumbnail", "severity", "warn", "code", 4204, "box_id", boxID, "error", err.Error())
			return
		}

		result, err := generateMissingThumbnailsForBox(uploadService, logger, box)
		if err != nil {
			logger.Warn("thumbnail one-shot job failed", "source", "thumbnail", "severity", "warn", "code", 4205, "box_id", boxID, "error", err.Error())
			return
		}
		if result.Generated > 0 || result.Failed > 0 {
			logger.Info("thumbnail one-shot job complete", "source", "thumbnail", "severity", "user_activity", "code", 2205, "box_id", boxID, "generated", result.Generated, "failed", result.Failed)
		}
	}()
}

func newThumbnailsJob(cfg config.Config, logger *slog.Logger, uploadService *services.UploadService) job {
	return job{
		name:     "thumbnail",
		enabled:  cfg.ThumbnailEnabled,
		interval: cfg.ThumbnailEvery,
		run: func() {
			result, err := generateMissingThumbnails(uploadService, logger)
			if err != nil {
				logger.Warn("thumbnail job failed", "source", "thumbnail", "severity", "warn", "code", 4203, "error", err.Error())
				return
			}
			if result.Generated > 0 || result.Failed > 0 {
				logger.Info("thumbnail job complete", "source", "thumbnail", "severity", "user_activity", "code", 2204, "generated", result.Generated, "failed", result.Failed)
			}
		},
	}
}

func RunThumbnailsNow(uploadService *services.UploadService, logger *slog.Logger) (ThumbnailJobResult, error) {
	return generateMissingThumbnails(uploadService, logger)
}

func generateMissingThumbnails(uploadService *services.UploadService, logger *slog.Logger) (ThumbnailJobResult, error) {
	boxes, err := uploadService.ListBoxes(0)
	if err != nil {
		return ThumbnailJobResult{}, err
	}

	var result ThumbnailJobResult
	now := time.Now().UTC()
	for _, box := range boxes {
		if !box.ExpiresAt.After(now) {
			continue
		}

		boxResult, err := generateMissingThumbnailsForBox(uploadService, logger, box)
		result.Scanned += boxResult.Scanned
		result.Generated += boxResult.Generated
		result.Failed += boxResult.Failed
		if err != nil {
			return result, err
		}
	}

	return result, nil
}

func generateMissingThumbnailsForBox(uploadService *services.UploadService, logger *slog.Logger, box services.Box) (ThumbnailJobResult, error) {
	var result ThumbnailJobResult
	if !box.ExpiresAt.After(time.Now().UTC()) {
		return result, nil
	}

	changed := false
	for i := range box.Files {
		file := &box.Files[i]
		if file.Thumbnail != "" || !needsThumbnail(*file) {
			continue
		}
		result.Scanned++

		thumbnail, err := generateThumbnail(uploadService, box, *file)
		if err != nil {
			logger.Warn("thumbnail generation failed", "source", "thumbnail", "severity", "warn", "code", 4101, "file_id", file.ID, "error", err.Error())
			result.Failed++
			continue
		}
		if thumbnail == "" {
			result.Failed++
			continue
		}

		file.Thumbnail = thumbnail
		changed = true
		result.Generated++
	}

	if changed {
		if err := uploadService.SaveBox(box); err != nil {
			return result, err
		}
	}
	return result, nil
}

func needsThumbnail(file services.File) bool {
	return file.PreviewKind == "image" || file.PreviewKind == "video" || isTextThumbnailCandidate(file)
}

func NeedsThumbnail(file services.File) bool {
	return needsThumbnail(file)
}

func GenerateThumbnailForFile(uploadService *services.UploadService, box services.Box, file services.File) (string, error) {
	return generateThumbnail(uploadService, box, file)
}

func generateThumbnail(uploadService *services.UploadService, box services.Box, file services.File) (string, error) {
	thumbnailName := "@thumb@" + file.ID + ".jpg"
	object, err := uploadService.OpenFileObject(context.Background(), box, file)
	if err != nil {
		return "", err
	}
	defer object.Body.Close()

	switch {
	case strings.HasPrefix(file.ContentType, "image/"):
		data, err := createImageThumbnail(object.Body)
		if err != nil {
			return "", err
		}
		_, err = uploadService.PutThumbnailObject(context.Background(), box, thumbnailName, bytes.NewReader(data), int64(len(data)), "image/jpeg")
		return thumbnailName, err
	case strings.HasPrefix(file.ContentType, "video/"):
		data, err := createVideoThumbnail(object.Body)
		if err != nil {
			return "", err
		}
		_, err = uploadService.PutThumbnailObject(context.Background(), box, thumbnailName, bytes.NewReader(data), int64(len(data)), "image/jpeg")
		return thumbnailName, err
	case isTextThumbnailCandidate(file):
		data, err := createTextThumbnail(file, object.Body)
		if err != nil {
			return "", err
		}
		_, err = uploadService.PutThumbnailObject(context.Background(), box, thumbnailName, bytes.NewReader(data), int64(len(data)), "image/jpeg")
		return thumbnailName, err
	default:
		return "", nil
	}
}

func isTextThumbnailCandidate(file services.File) bool {
	contentType := strings.ToLower(strings.TrimSpace(file.ContentType))
	if i := strings.IndexByte(contentType, ';'); i >= 0 {
		contentType = strings.TrimSpace(contentType[:i])
	}
	if strings.HasPrefix(contentType, "text/") {
		return true
	}
	switch contentType {
	case "application/json", "application/ld+json", "application/xml", "application/javascript", "application/x-javascript", "application/markdown":
		return true
	}
	ext := strings.TrimPrefix(strings.ToLower(filepath.Ext(file.Name)), ".")
	switch ext {
	case "c", "cc", "conf", "cpp", "cs", "css", "csv", "diff", "dockerfile", "go", "h", "hpp", "htm", "html", "ini", "java", "js", "json", "jsx", "kt", "log", "lua", "md", "mdown", "markdown", "php", "pl", "properties", "py", "rb", "rs", "sh", "sql", "swift", "toml", "ts", "tsx", "txt", "xml", "yaml", "yml", "zig":
		return true
	default:
		return false
	}
}

func createImageThumbnail(source io.Reader) ([]byte, error) {
	img, _, err := image.Decode(source)
	if err != nil {
		return nil, err
	}

	thumb := resizeNearest(img, 360, 240)
	var target bytes.Buffer
	err = jpeg.Encode(&target, thumb, &jpeg.Options{Quality: 82})
	if err != nil {
		return nil, err
	}
	return target.Bytes(), nil
}

func createVideoThumbnail(source io.Reader) ([]byte, error) {
	sourceFile, err := os.CreateTemp("", "warpbox-video-*")
	if err != nil {
		return nil, err
	}
	defer os.Remove(sourceFile.Name())
	if _, err := io.Copy(sourceFile, source); err != nil {
		sourceFile.Close()
		return nil, err
	}
	if err := sourceFile.Close(); err != nil {
		return nil, err
	}
	targetFile, err := os.CreateTemp("", "warpbox-thumb-*.jpg")
	if err != nil {
		return nil, err
	}
	targetPath := targetFile.Name()
	targetFile.Close()
	defer os.Remove(targetPath)
	if err := exec.Command("ffmpeg", "-y", "-loglevel", "error", "-ss", "00:00:01", "-i", sourceFile.Name(), "-frames:v", "1", "-vf", "scale=360:-1", targetPath).Run(); err != nil {
		return nil, err
	}
	return os.ReadFile(targetPath)
}

func createTextThumbnail(file services.File, source io.Reader) ([]byte, error) {
	data, err := io.ReadAll(io.LimitReader(source, 128*1024))
	if err != nil {
		return nil, err
	}
	sourceText := strings.ReplaceAll(string(data), "\r\n", "\n")
	sourceText = strings.ReplaceAll(sourceText, "\r", "\n")

	mode := textThumbnailMode(file)
	title := strings.ToUpper(mode)
	var lines []string
	if mode == "HTML" {
		lines = renderedHTMLThumbnailLines(sourceText)
	} else if mode == "MARKDOWN" {
		lines = renderedMarkdownThumbnailLines(sourceText)
	} else {
		title = "CODE"
		lines = codeThumbnailLines(sourceText)
	}
	return renderTextThumbnail(file.Name, title, lines), nil
}

func textThumbnailMode(file services.File) string {
	contentType := strings.ToLower(strings.TrimSpace(file.ContentType))
	if i := strings.IndexByte(contentType, ';'); i >= 0 {
		contentType = strings.TrimSpace(contentType[:i])
	}
	ext := strings.TrimPrefix(strings.ToLower(filepath.Ext(file.Name)), ".")
	if ext == "html" || ext == "htm" || contentType == "text/html" {
		return "HTML"
	}
	if ext == "md" || ext == "mdown" || ext == "markdown" || contentType == "text/markdown" || contentType == "application/markdown" {
		return "MARKDOWN"
	}
	return "CODE"
}

func renderedHTMLThumbnailLines(source string) []string {
	text := regexp.MustCompile(`(?is)<script[^>]*>.*?</script>`).ReplaceAllString(source, " ")
	text = regexp.MustCompile(`(?is)<style[^>]*>.*?</style>`).ReplaceAllString(text, " ")
	text = regexp.MustCompile(`(?i)</?(p|div|section|article|main|header|footer|br|li|ul|ol|h[1-6]|tr|table|blockquote|pre|code)[^>]*>`).ReplaceAllString(text, "\n")
	text = regexp.MustCompile(`(?s)<[^>]+>`).ReplaceAllString(text, " ")
	text = html.UnescapeString(text)
	return documentThumbnailLines(text)
}

func renderedMarkdownThumbnailLines(source string) []string {
	text := regexp.MustCompile("(?s)```.*?```").ReplaceAllStringFunc(source, func(block string) string {
		block = strings.Trim(block, "` \n\t")
		lines := strings.Split(block, "\n")
		if len(lines) > 1 {
			lines = lines[1:]
		}
		return "\n" + strings.Join(lines, "\n") + "\n"
	})
	text = regexp.MustCompile(`(?m)^#{1,6}\s*`).ReplaceAllString(text, "")
	text = regexp.MustCompile(`!\[([^\]]*)\]\([^)]+\)`).ReplaceAllString(text, "$1")
	text = regexp.MustCompile(`\[([^\]]+)\]\([^)]+\)`).ReplaceAllString(text, "$1")
	text = regexp.MustCompile("`([^`]+)`").ReplaceAllString(text, "$1")
	text = strings.NewReplacer("**", "", "__", "", "*", "", "_", "", "~~", "").Replace(text)
	return documentThumbnailLines(text)
}

func documentThumbnailLines(source string) []string {
	source = regexp.MustCompile(`[ \t]+`).ReplaceAllString(source, " ")
	rawLines := strings.Split(source, "\n")
	lines := make([]string, 0, 9)
	for _, raw := range rawLines {
		raw = strings.TrimSpace(raw)
		if raw == "" {
			continue
		}
		for _, line := range wrapTextThumbnailLine(raw, 43) {
			lines = append(lines, line)
			if len(lines) >= 9 {
				return lines
			}
		}
	}
	if len(lines) == 0 {
		return []string{"Rendered preview is empty."}
	}
	return lines
}

func codeThumbnailLines(source string) []string {
	rawLines := strings.Split(source, "\n")
	lines := make([]string, 0, 10)
	for _, raw := range rawLines {
		raw = strings.ReplaceAll(raw, "\t", "  ")
		raw = strings.TrimRight(raw, " ")
		if strings.TrimSpace(raw) == "" && len(lines) == 0 {
			continue
		}
		if len(raw) > 48 {
			raw = raw[:45] + "..."
		}
		lines = append(lines, raw)
		if len(lines) >= 10 {
			break
		}
	}
	if len(lines) == 0 {
		return []string{"(empty file)"}
	}
	return lines
}

func renderTextThumbnail(name, mode string, lines []string) []byte {
	canvas := image.NewRGBA(image.Rect(0, 0, 360, 240))
	drawSolid(canvas, canvas.Bounds(), color.RGBA{R: 0x0b, G: 0x0b, B: 0x16, A: 0xff})
	drawSolid(canvas, image.Rect(10, 10, 350, 230), color.RGBA{R: 0x17, G: 0x14, B: 0x2d, A: 0xff})
	drawSolid(canvas, image.Rect(10, 10, 350, 16), color.RGBA{R: 0xa7, G: 0x8b, B: 0xfa, A: 0xff})

	face := basicfont.Face7x13
	drawThumbText(canvas, face, trimThumbnailText(name, 38), 22, 36, color.RGBA{R: 0xf5, G: 0xf3, B: 0xff, A: 0xff})
	drawThumbText(canvas, face, mode+" PREVIEW", 22, 55, color.RGBA{R: 0x67, G: 0xe8, B: 0xf9, A: 0xff})

	codePane := image.Rect(22, 72, 338, 210)
	if mode == "CODE" {
		drawSolid(canvas, codePane, color.RGBA{R: 0x0f, G: 0x11, B: 0x1a, A: 0xff})
	} else {
		drawSolid(canvas, codePane, color.RGBA{R: 0x21, G: 0x1b, B: 0x3e, A: 0xff})
	}

	y := 91
	for _, line := range lines {
		drawThumbText(canvas, face, line, 32, y, color.RGBA{R: 0xf8, G: 0xfa, B: 0xfc, A: 0xff})
		y += 14
		if y > 202 {
			break
		}
	}

	var target bytes.Buffer
	_ = jpeg.Encode(&target, canvas, &jpeg.Options{Quality: 84})
	return target.Bytes()
}

func drawSolid(dst *image.RGBA, rect image.Rectangle, c color.Color) {
	draw.Draw(dst, rect, &image.Uniform{c}, image.Point{}, draw.Src)
}

func drawThumbText(dst *image.RGBA, face font.Face, text string, x, y int, c color.Color) {
	d := font.Drawer{
		Dst:  dst,
		Src:  image.NewUniform(c),
		Face: face,
		Dot:  fixed.P(x, y),
	}
	d.DrawString(text)
}

func wrapTextThumbnailLine(text string, maxChars int) []string {
	if len(text) <= maxChars {
		return []string{text}
	}
	words := strings.Fields(text)
	if len(words) == 0 {
		return []string{text[:maxChars-3] + "..."}
	}
	lines := []string{}
	current := ""
	for _, word := range words {
		if current == "" {
			current = word
			continue
		}
		if len(current)+1+len(word) <= maxChars {
			current += " " + word
			continue
		}
		lines = append(lines, trimThumbnailText(current, maxChars))
		current = word
	}
	if current != "" {
		lines = append(lines, trimThumbnailText(current, maxChars))
	}
	return lines
}

func trimThumbnailText(text string, maxChars int) string {
	if len(text) <= maxChars {
		return text
	}
	if maxChars <= 3 {
		return text[:maxChars]
	}
	return strings.TrimSpace(text[:maxChars-3]) + "..."
}

func resizeNearest(src image.Image, maxWidth, maxHeight int) *image.RGBA {
	bounds := src.Bounds()
	width := bounds.Dx()
	height := bounds.Dy()
	if width <= 0 || height <= 0 {
		return image.NewRGBA(image.Rect(0, 0, 1, 1))
	}

	scale := min(float64(maxWidth)/float64(width), float64(maxHeight)/float64(height))
	if scale > 1 {
		scale = 1
	}
	targetWidth := max(1, int(float64(width)*scale))
	targetHeight := max(1, int(float64(height)*scale))
	dst := image.NewRGBA(image.Rect(0, 0, targetWidth, targetHeight))

	for y := 0; y < targetHeight; y++ {
		for x := 0; x < targetWidth; x++ {
			srcX := bounds.Min.X + int(float64(x)/scale)
			srcY := bounds.Min.Y + int(float64(y)/scale)
			dst.Set(x, y, src.At(srcX, srcY))
		}
	}

	return dst
}