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package preview

import (
	"strings"

	"github.com/charmbracelet/lipgloss"
)

// SGR escapes. The header writes them by hand rather than through lipgloss so
// the colors survive a non-TTY renderer (tests, pipes) exactly like the rest of
// this package's output, which glamour also emits unconditionally.
const (
	sgrReset  = "\x1b[0m"
	sgrBold   = "\x1b[1m"
	sgrItalic = "\x1b[3m"
)

// propIndent is the left inset of the properties block, and propGap the space
// between the key column and the value column.
const (
	propIndent = "  "
	propGap    = "  "
)

// renderHeader draws the document header that sits above the glamour body: the
// doc name as a full-width bar in the heading color (an H1 block that spans the
// column), then the frontmatter properties as a tight, aligned, italic list —
// dim keys, italic values, one line each, no rules and no blank lines between.
// Returns "" when there is neither a name nor a property.
func (m *Model) renderHeader(title string, props []prop) string {
	if title == "" && len(props) == 0 {
		return ""
	}
	width := m.width
	if width < 1 {
		width = 80
	}
	var b strings.Builder
	if title != "" {
		b.WriteString(m.titleBar(title, width))
		b.WriteByte('\n')
	}
	if len(props) > 0 {
		if title != "" {
			b.WriteByte('\n') // one blank line under the name
		}
		b.WriteString(m.propList(props, width))
	}
	return b.String()
}

// titleBar renders the doc name as a bold, full-width filled block: the heading
// color behind, a legible text color on top. Without a themed heading color it
// falls back to bold text.
func (m *Model) titleBar(title string, width int) string {
	pad := width - lipgloss.Width(title) - 2 // one space each side
	if pad < 0 {
		title = truncate(title, width-2)
		pad = 0
	}
	line := " " + title + " " + strings.Repeat(" ", pad)
	open := sgrBold
	if bg := hexToRGB(m.colors.Heading); bg != "" {
		open += "\x1b[38;2;" + hexToRGB(legibleText(m.colors.Heading)) + ";48;2;" + bg + "m"
	}
	return open + line + sgrReset
}

// propList renders the aligned key/value rows. Keys are padded to the widest
// key so the values form a column; long values wrap with a hanging indent that
// keeps them inside that column.
func (m *Model) propList(props []prop, width int) string {
	keyw := 0
	for _, p := range props {
		if w := lipgloss.Width(p.key); w > keyw {
			keyw = w
		}
	}
	valLeft := len(propIndent) + keyw + len(propGap)
	valWidth := max(width-valLeft, 8)
	keyOpen, valOpen := m.propStyles()

	var b strings.Builder
	for _, p := range props {
		b.WriteString(propIndent)
		b.WriteString(keyOpen)
		b.WriteString(p.key)
		b.WriteString(strings.Repeat(" ", keyw-lipgloss.Width(p.key)))
		b.WriteString(sgrReset)
		b.WriteString(propGap)
		for i, ln := range wrapWords(p.val, valWidth) {
			if i > 0 {
				b.WriteString(strings.Repeat(" ", valLeft))
			}
			b.WriteString(valOpen)
			b.WriteString(ln)
			b.WriteString(sgrReset)
			b.WriteByte('\n')
		}
		if p.val == "" {
			b.WriteByte('\n')
		}
	}
	return b.String()
}

// propStyles returns the SGR prefixes for a property key (dim) and value
// (italic), falling back to plain text when the theme colors are unset.
func (m *Model) propStyles() (key, val string) {
	if c := hexToRGB(m.colors.Muted); c != "" {
		key = "\x1b[38;2;" + c + "m"
	}
	val = sgrItalic
	if c := hexToRGB(m.colors.Text); c != "" {
		val += "\x1b[38;2;" + c + "m"
	}
	return key, val
}

// wrapWords greedily wraps text to width, breaking on spaces. An empty string
// yields no lines.
func wrapWords(s string, width int) []string {
	if s == "" {
		return nil
	}
	var lines []string
	cur := ""
	for _, w := range strings.Fields(s) {
		switch {
		case cur == "":
			cur = w
		case lipgloss.Width(cur)+1+lipgloss.Width(w) <= width:
			cur += " " + w
		default:
			lines = append(lines, cur)
			cur = w
		}
	}
	if cur != "" {
		lines = append(lines, cur)
	}
	return lines
}

// truncate cuts s to at most width display cells, ending in an ellipsis.
func truncate(s string, width int) string {
	if width < 1 {
		return ""
	}
	if lipgloss.Width(s) <= width {
		return s
	}
	r := []rune(s)
	for len(r) > 0 && lipgloss.Width(string(r))+1 > width {
		r = r[:len(r)-1]
	}
	return string(r) + "…"
}