package main

import (
	"fmt"
	"html/template"
	"io"
	"io/fs"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	_ "net/http/pprof"

	"github.com/adrg/frontmatter"
	"github.com/gomarkdown/markdown"
	"github.com/gomarkdown/markdown/ast"
	"github.com/gomarkdown/markdown/html"
	"github.com/gomarkdown/markdown/parser"
)

type TOCItem struct {
	Level int
	Text  string
	ID    string
}

type Page struct {
	Title   string
	Content template.HTML
	TOC     []TOCItem
}

type Post struct {
	Title string
}
type Frontmatter struct {
	Title string   `yaml:"title"`
	Date  string   `yaml:"date"`
	Tags  []string `yaml:"tags"`
}

func main() {
	contentDir := "./content"
	outputDir := "./output"

	posts := make([]Post, 0)

	themeName := "modern-light"

	args := os.Args
	if len(args) > 1 {
		switch args[1] {
		case "serve":
			copyFile("./themes/"+themeName+".css", "./output/style.css")

			fs := http.FileServer(http.Dir("./output/"))
			http.Handle("/", fs)

			log.Println("Serving on http://localhost:8000")

			err := http.ListenAndServe(":8000", nil)
			if err != nil {
				log.Fatalf("Error occured %s\n", err)
			}
		}
	}

	summaries := make([]PostSummary, 0)

	err := filepath.WalkDir(contentDir, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		if d.IsDir() {
			return nil
		}

		if strings.HasSuffix(d.Name(), ".md") {
			fmt.Println("Processing:", path)

			matter, htmlContent, toc := convertToHtml(path)
			slug := strings.TrimSuffix(d.Name(), ".md")
			summaries = append(summaries, PostSummary{
				Title: matter.Title,
				Slug:  slug,
				Date:  matter.Date,
				Tags:  matter.Tags,
			})

			posts = append(posts, Post{Title: matter.Title})
			// fmt.Println("Appended post", posts)
			newPage := Page{
				Title:   matter.Title,
				Content: template.HTML(htmlContent),
				TOC:     toc,
			}

			tmpl, err := template.ParseFiles("./layout.html")
			if err != nil {
				log.Fatalf("Error parsing template: %s", err)
			}

			relPath, err := filepath.Rel(contentDir, path)
			if err != nil {
				log.Fatalf("Error computing relative path: %s", err)
			}
			// test.md -> test.html
			// test.md -> test/index.html
			outputFilePath := filepath.Join(outputDir, strings.Replace(relPath, ".md", "/index.html", 1))

			err = os.MkdirAll(filepath.Dir(outputFilePath), 0o755)
			if err != nil {
				log.Fatalf("Error creating directories: %s", err)
			}

			outputFile, err := os.Create(outputFilePath)
			if err != nil {
				log.Fatalf("Error creating output file: %s", err)
			}
			defer outputFile.Close()

			err = tmpl.Execute(outputFile, newPage)
			if err != nil {
				log.Fatalf("Error generating output content: %s", err)
			}
		}

		return nil
	})
	if err != nil {
		log.Fatalf("Error walking directory: %s", err)
	}

	fmt.Println("All files processed!")

	fmt.Println(posts)

	renderHomePage(summaries, outputDir)
}

func convertToHtml(path string) (Frontmatter, []byte, []TOCItem) {
	md, err := os.ReadFile(path)
	if err != nil {
		log.Fatalf("Error reading %s: %s", path, err)
	}

	var matter Frontmatter
	rest, err := frontmatter.Parse(strings.NewReader(string(md)), &matter)
	if err != nil {
		log.Fatalf("Error parsing frontmatter: %s", err)
	}

	extensions := parser.CommonExtensions | parser.AutoHeadingIDs
	p := parser.NewWithExtensions(extensions)

	doc := p.Parse(rest)

	var toc []TOCItem

	ast.WalkFunc(doc, func(node ast.Node, entering bool) ast.WalkStatus {
		if heading, ok := node.(*ast.Heading); ok && entering {
			text := extractText(heading)
			id := string(heading.HeadingID)

			toc = append(toc, TOCItem{
				Level: heading.Level,
				Text:  text,
				ID:    id,
			})
		}
		return ast.GoToNext
	})

	renderer := html.NewRenderer(html.RendererOptions{
		Flags: html.CommonFlags,
	})

	output := markdown.Render(doc, renderer)

	return matter, output, toc
}

func copyFile(src, dst string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()

	if err := os.MkdirAll(filepath.Dir(dst), os.ModePerm); err != nil {
		return err
	}

	out, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer out.Close()

	_, err = io.Copy(out, in)
	return err
}

func extractText(h *ast.Heading) string {
	var text string
	ast.WalkFunc(h, func(node ast.Node, entering bool) ast.WalkStatus {
		if leaf, ok := node.(*ast.Text); ok && entering {
			text += string(leaf.Literal)
		}
		return ast.GoToNext
	})
	return text
}

type PostSummary struct {
	Title string
	Slug  string   // derived from filename, e.g. "my-post" from "my-post.md"
	Date  string   // from frontmatter, e.g. "Mar 2026"
	Tags  []string // from frontmatter (optional)
}

type HomePage struct {
	SiteTitle  string
	AuthorName string
	AuthorRole string
	AuthorBio  string
	Year       int
	Posts      []PostSummary // sorted newest-first
}

func renderHomePage(summaries []PostSummary, outputDir string) {
	sort.Slice(summaries, func(i, j int) bool {
		return summaries[i].Date > summaries[j].Date
	})

	for i, p := range summaries {
		if t, err := time.Parse("2006-01-02", p.Date); err == nil {
			summaries[i].Date = t.Format("Jan 2006")
		}
	}

	data := HomePage{
		SiteTitle:  "himanshu.co",
		AuthorName: "Himanshu Sardana",
		AuthorRole: "Student",
		AuthorBio:  "20 y/o linux enthusiast & software engineer",
		Year:       time.Now().Year(),
		Posts:      summaries,
	}

	tmpl, err := template.ParseFiles("./home.html")
	if err != nil {
		log.Fatalf("Error parsing home template: %s", err)
	}

	outPath := filepath.Join(outputDir, "index.html")
	if err := os.MkdirAll(filepath.Dir(outPath), 0o755); err != nil {
		log.Fatalf("Error creating output dir: %s", err)
	}
	f, err := os.Create(outPath)
	if err != nil {
		log.Fatalf("Error creating index.html: %s", err)
	}
	defer f.Close()

	if err := tmpl.Execute(f, data); err != nil {
		log.Fatalf("Error rendering home page: %s", err)
	}
	fmt.Println("Home page written to", outPath)
}