package main

import (
	"html"
	"net/http"
	"os"
	"path/filepath"
	"strings"
)

func ChangelogPage(w http.ResponseWriter, r *http.Request) {
	markdown := readChangelog()
	body := `
<header class="tool-header">
  <h2 class="tool-title">Changelog</h2>
  <p class="tool-description">Loaded from README.md.</p>
</header>
<section class="tool-panel changelog-panel">
  <div class="panel-body changelog-content">
` + renderChangelogMarkdown(markdown) + `
  </div>
</section>
<style>
  .changelog-panel { max-width: 840px; }
  .changelog-content h1 { margin: 0 0 14px; font-size: 20px; line-height: 1.25; }
  .changelog-content h2 { margin: 18px 0 8px; padding-top: 12px; border-top: 1px solid #333; font-size: 15px; line-height: 1.3; }
  .changelog-content ul { margin: 6px 0 12px; padding-left: 20px; }
  .changelog-content li { margin: 4px 0; line-height: 1.45; }
  .changelog-content p { margin: 8px 0; line-height: 1.5; }
</style>`

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_, _ = w.Write([]byte(Page("/changelog", "Changelog", body)))
}

func readChangelog() string {
	for _, start := range changelogSearchRoots() {
		for _, candidate := range changelogCandidates(start) {
			data, err := os.ReadFile(candidate)
			if err == nil {
				return string(data)
			}
		}
	}
	return "# Changelog\n\nREADME.md was not found."
}

func changelogSearchRoots() []string {
	roots := []string{}
	if wd, err := os.Getwd(); err == nil {
		roots = append(roots, wd)
	}
	roots = append(roots, appDir())
	return roots
}

func changelogCandidates(start string) []string {
	candidates := []string{}
	dir := filepath.Clean(start)
	for i := 0; i < 5; i++ {
		candidates = append(candidates, filepath.Join(dir, "README.md"))
		parent := filepath.Dir(dir)
		if parent == dir {
			break
		}
		dir = parent
	}
	return candidates
}

func renderChangelogMarkdown(markdown string) string {
	lines := strings.Split(strings.ReplaceAll(markdown, "\r\n", "\n"), "\n")
	var out strings.Builder
	inList := false
	closeList := func() {
		if inList {
			out.WriteString("</ul>")
			inList = false
		}
	}

	for _, rawLine := range lines {
		line := strings.TrimSpace(rawLine)
		if line == "" {
			closeList()
			continue
		}
		if strings.HasPrefix(line, "### ") {
			closeList()
			out.WriteString("<h2>" + html.EscapeString(strings.TrimSpace(line[4:])) + "</h2>")
			continue
		}
		if strings.HasPrefix(line, "## ") {
			closeList()
			out.WriteString("<h2>" + html.EscapeString(strings.TrimSpace(line[3:])) + "</h2>")
			continue
		}
		if strings.HasPrefix(line, "# ") {
			closeList()
			out.WriteString("<h1>" + html.EscapeString(strings.TrimSpace(line[2:])) + "</h1>")
			continue
		}
		if strings.HasPrefix(line, "- ") {
			if !inList {
				out.WriteString("<ul>")
				inList = true
			}
			out.WriteString("<li>" + html.EscapeString(strings.TrimSpace(line[2:])) + "</li>")
			continue
		}
		closeList()
		out.WriteString("<p>" + html.EscapeString(line) + "</p>")
	}
	closeList()
	return out.String()
}