package views

import (
	"strings"
	"sync"

	"github.com/charmbracelet/glamour"
	"github.com/charmbracelet/glamour/styles"
	"github.com/charmbracelet/lipgloss"
	"github.com/muesli/termenv"

	"task/internal/ticket"
)

type mdCacheKey struct {
	width int
	src   string
}

var (
	mdMu       sync.Mutex
	mdRenderer *glamour.TermRenderer
	mdWidth    int
	mdCache    = map[mdCacheKey]string{}
)

// RenderMarkdown renders Markdown to ANSI using a cached glamour renderer.
//
// Important: we intentionally use a fixed dark style — NOT WithAutoStyle().
// AutoStyle calls termenv.HasDarkBackground(), which sends an OSC query to the
// terminal and waits up to ~5s for a reply. In Cursor/some PTYs that reply
// never arrives, so the TUI appears to hang on startup (first selected ticket
// with a description triggers the renderer in ensureVisible/View).
func RenderMarkdown(src string, width int) string {
	if src == "" {
		return ""
	}
	if width < 20 {
		width = 20
	}

	key := mdCacheKey{width: width, src: src}
	mdMu.Lock()
	defer mdMu.Unlock()

	if out, ok := mdCache[key]; ok {
		return out
	}

	r, err := getRenderer(width)
	if err != nil {
		return src
	}
	out, err := r.Render(src)
	if err != nil {
		return src
	}
	for len(out) > 0 && (out[len(out)-1] == '\n' || out[len(out)-1] == ' ') {
		out = out[:len(out)-1]
	}
	if len(mdCache) > 128 {
		mdCache = map[mdCacheKey]string{}
	}
	mdCache[key] = out
	return out
}

func getRenderer(width int) (*glamour.TermRenderer, error) {
	if mdRenderer != nil && mdWidth == width {
		return mdRenderer, nil
	}
	r, err := glamour.NewTermRenderer(
		glamour.WithStyles(styles.DarkStyleConfig),
		glamour.WithWordWrap(width),
		glamour.WithColorProfile(termenv.ANSI256),
		glamour.WithEmoji(),
	)
	if err != nil {
		return nil, err
	}
	mdRenderer = r
	mdWidth = width
	return r, nil
}

// RenderDescription renders ticket Markdown with interactive task-list items.
// checklistCursor is the 0-based index among checkboxes (highlight); ignored when
// there are none.
func RenderDescription(src string, width int, checklistCursor int) string {
	if strings.TrimSpace(src) == "" {
		return ""
	}
	boxes := ticket.ListCheckboxes(src)
	if len(boxes) == 0 {
		return RenderMarkdown(src, width)
	}

	boxByLine := make(map[int]int, len(boxes))
	for i, b := range boxes {
		boxByLine[b.Line] = i
	}

	lines := strings.Split(src, "\n")
	var parts []string
	var mdBuf []string
	flushMD := func() {
		if len(mdBuf) == 0 {
			return
		}
		block := strings.Join(mdBuf, "\n")
		if strings.TrimSpace(block) != "" {
			parts = append(parts, RenderMarkdown(block, width))
		}
		mdBuf = nil
	}

	for i, line := range lines {
		if bi, ok := boxByLine[i]; ok {
			flushMD()
			parts = append(parts, renderCheckboxLine(boxes[bi], bi == checklistCursor, width))
			continue
		}
		mdBuf = append(mdBuf, line)
	}
	flushMD()
	if len(parts) == 0 {
		return ""
	}
	return lipgloss.JoinVertical(lipgloss.Left, parts...)
}

func renderCheckboxLine(box ticket.Checkbox, selected bool, width int) string {
	// ASCII markers — widely supported; bold + padding reads a notch bigger.
	mark := "[ ]"
	if box.Checked {
		mark = "[x]"
	}
	prefix := "  "
	if selected {
		prefix = "> "
	}
	label := strings.TrimSpace(box.Text)
	avail := max(10, width) - lipgloss.Width(prefix+mark+" ")
	label = truncateOneLine(label, avail)

	markStyle := lipgloss.NewStyle().Bold(true)
	labelStyle := lipgloss.NewStyle()
	if selected {
		markStyle = markStyle.Foreground(lipgloss.Color("39"))
		labelStyle = labelStyle.Bold(true).Foreground(lipgloss.Color("39"))
	} else if box.Checked {
		labelStyle = labelStyle.Faint(true)
	}
	line := prefix + markStyle.Render(mark) + " " + labelStyle.Render(label)
	return lipgloss.NewStyle().Width(max(10, width)).Render(line)
}

// ClearMarkdownCache drops cached renders (e.g. after theme change).
func ClearMarkdownCache() {
	mdMu.Lock()
	defer mdMu.Unlock()
	mdCache = map[mdCacheKey]string{}
	mdRenderer = nil
	mdWidth = 0
}