package internal

import (
	"fmt"
	"strings"

	"charm.land/lipgloss/v2"
	"u-tabs/internal/style"
)

// --- 技能 tab 三栏渲染 ---

func (m *Model) renderSkills() string {
	if !m.Skills.Loaded && !m.Skills.Scanning {
		return style.ScanningStyle.Render("  press Tab to load skills...")
	}
	if m.Skills.Scanning {
		return style.ScanningStyle.Render("  scanning skills...")
	}
	if len(m.Skills.Skills) == 0 {
		return style.SubtitleStyle.Render("  no skills found in ~/.claude/skills/")
	}

	avail := m.width - 8
	skillW := max(18, avail*20/100)
	fileW := max(22, avail*28/100)
	contentW := avail - skillW - fileW
	listH := max(3, m.height-7)

	skillCw := skillW - 2
	fileCw := fileW - 2
	contentCw := contentW - 2

	skillLines := m.skillsListLines(skillCw, listH-1)
	fileLines := m.skillsFileLines(fileCw, listH-1)
	contentLines := m.skillsContentLines(contentCw, listH-1)

	maxRows := min(listH-1, max(max(len(skillLines), len(fileLines)), len(contentLines)))

	panelSty := lipgloss.NewStyle().
		Border(lipgloss.RoundedBorder()).
		BorderForeground(style.BgPanel)

	skillBorderFg := style.BgPanel
	if m.Skills.FocusPanel == 0 {
		skillBorderFg = style.Accent
	}
	fileBorderFg := style.BgPanel
	if m.Skills.FocusPanel == 1 {
		fileBorderFg = style.Accent
	}

	skillBox := panelSty.BorderForeground(skillBorderFg).Width(skillW).Render(
		style.DetailTitle.Render("skills") + "\n" + padLinesTo(skillLines, skillCw, maxRows))
	fileBox := panelSty.BorderForeground(fileBorderFg).Width(fileW).Render(
		style.DetailTitle.Render("files") + "\n" + padLinesTo(fileLines, fileCw, maxRows))
	contentBox := panelSty.BorderForeground(style.BgPanel).Width(contentW).Render(
		style.DetailTitle.Render("content") + "\n" + padLinesTo(contentLines, contentCw, maxRows))

	return lipgloss.JoinHorizontal(lipgloss.Top, skillBox, " ", fileBox, " ", contentBox)
}

func (m *Model) skillsListLines(w, listH int) []string {
	skills := m.Skills.Skills
	if len(skills) == 0 {
		return []string{style.DimFg.Render(fitWidth("  empty", w))}
	}
	// 先为所有技能累积全部行（含描述行），再按行数视口切片，
	// 避免按条目数计算视口导致变长行撑爆面板
	type skillBlock struct {
		lines []string
	}
	var blocks []skillBlock
	totalLines := 0
	curLineOffset := 0

	for i, sk := range skills {
		cur := " "
		if i == m.Skills.SkillCur {
			cur = "▸"
		}
		line := fmt.Sprintf(" %s %s", cur, sk.Name)
		sty := style.NormStyle
		if i == m.Skills.SkillCur && m.Skills.FocusPanel == 0 {
			sty = style.SelStyle
		}
		blockLines := []string{sty.Render(padRightByWidth(truncateByWidth(line, w), w))}
		// 如果有描述，追加一行
		if sk.Description != "" {
			descLine := "   " + sk.Description
			descSty := style.DimFg
			if i == m.Skills.SkillCur && m.Skills.FocusPanel == 0 {
				descSty = style.SelStyle
			}
			blockLines = append(blockLines, descSty.Render(padRightByWidth(truncateByWidth(descLine, w), w)))
		}
		if i == m.Skills.SkillCur {
			curLineOffset = totalLines
		}
		totalLines += len(blockLines)
		blocks = append(blocks, skillBlock{lines: blockLines})
	}

	start, end := viewport(curLineOffset, totalLines, listH)

	var allLines []string
	for _, b := range blocks {
		allLines = append(allLines, b.lines...)
	}
	if end > len(allLines) {
		end = len(allLines)
	}
	return allLines[start:end]
}

func (m *Model) skillsFileLines(w, listH int) []string {
	flat := m.skillsFlattened()
	if len(flat) == 0 {
		return []string{style.DimFg.Render(fitWidth("  ← select skill", w))}
	}
	start, end := viewport(m.Skills.FileCur, len(flat), listH)
	var lines []string
	for i := start; i < end; i++ {
		fn := flat[i]
		indent := strings.Repeat("  ", fn.Depth)
		cur := " "
		if i == m.Skills.FileCur {
			cur = "▸"
		}
		prefix := "  "
		if fn.IsDir {
			if fn.Expanded {
				prefix = "▾ "
			} else {
				prefix = "▸ "
			}
		}
		display := indent + cur + prefix + fn.Name
		sty := style.NormStyle
		if fn.IsDir {
			sty = style.AccentFg
		}
		if i == m.Skills.FileCur && m.Skills.FocusPanel == 1 {
			sty = style.SelStyle
		}
		lines = append(lines, sty.Render(padRightByWidth(truncateByWidth(display, w), w)))
	}
	return lines
}

func (m *Model) skillsContentLines(w, listH int) []string {
	if m.Skills.ContentPath == "" {
		return []string{style.DimFg.Render(fitWidth("  ← select file to view", w))}
	}
	header := style.DetailTitle.Render(fitWidth(" "+m.Skills.ContentPath, w))
	sep := style.SepFg.Render(fitWidth(sepRunes(w), w))

	var lines []string
	lines = append(lines, header)
	lines = append(lines, sep)

	contentLines := strings.Split(m.Skills.Content, "\n")
	// 内容面板保留标题和分隔线，其余行按滚动偏移显示
	maxLines := max(0, listH-2)
	start := m.Skills.ContentScroll
	if start > len(contentLines) {
		start = len(contentLines)
	}
	end := min(len(contentLines), start+maxLines)
	for _, line := range contentLines[start:end] {
		lines = append(lines, style.NormStyle.Render(fitWidth(line, w)))
	}
	// 滚动到末尾时自动回收偏移，避免窗口缩小时空白
	if maxLines > 0 && m.Skills.ContentScroll > max(0, len(contentLines)-maxLines) {
		m.Skills.ContentScroll = max(0, len(contentLines)-maxLines)
	}
	return lines
}