package main

import (
	"bytes"
	"embed"
	"fmt"
	"html/template"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/alecthomas/kong"
	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing/object"
)

type RepoDir struct {
	Name        string
	Description string
	Owner       string
	LastCommit  time.Time
}

type RepoInfo struct {
	Name            string
	Description     string
	Url             string
	HasReadme       bool
	HasLicense      bool
	HasContributing bool
}

type CommitFile struct {
	Mode  string
	Path  string
	Name  string
	Lines int
}

//go:embed templates
var embedTmpl embed.FS
var funcMap = template.FuncMap{"inc": func(i int) int { return i + 1 }}

// ToDo: add a map function to generate the menu

func executeTemplate(name string, data any) ([]byte, error) {
	path := filepath.Join("templates", fmt.Sprintf("%s.html.tmpl", name))
	b, err := embedTmpl.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("cannot read embedded file %q: %w", path, err)
	}

	tmpl, err := template.New("").Funcs(funcMap).Parse(string(b))
	if err != nil {
		return nil, fmt.Errorf("cannot parse template %q: %w", path, err)
	}

	var strb bytes.Buffer
	if err := tmpl.Execute(&strb, data); err != nil {
		return nil, fmt.Errorf("cannot execute template %q: %w", path, err)
	}

	return strb.Bytes(), nil
}

func readFile(path string) (string, error) {
	if fi, err := os.Stat(path); err == nil && !fi.IsDir() {
		b, err := os.ReadFile(path)
		if err != nil {
			return "", fmt.Errorf("cannot read contents of file %q: %w", path, err)
		}
		return strings.TrimSpace(string(b)), nil
	}

	return "", nil
}

func readRepoFile(dirname, name string) (contents string, err error) {
	contents, err = readFile(filepath.Join(dirname, ".git", name))
	if err != nil {
		return
	}

	if contents == "" {
		contents, err = readFile(filepath.Join(dirname, name))
		return
	}
	return
}

func generateIndex(args []string) error {
	slog.Debug("Generating index", "args", args)

	repoDirs := []*RepoDir{}
	for _, dirname := range args {
		slog.Debug("Processing directory", "dirname", dirname)
		reponame := strings.TrimSuffix(filepath.Base(dirname), ".git")
		repoDir := &RepoDir{Name: reponame}

		// read description
		description, err := readRepoFile(dirname, "description")
		if err != nil {
			return fmt.Errorf("cannot read description for repository %q: %w", dirname, err)
		}
		repoDir.Description = description

		// read owner
		owner, err := readRepoFile(dirname, "owner")
		if err != nil {
			return fmt.Errorf("cannot read owner for repository %q: %w", dirname, err)
		}
		repoDir.Owner = owner

		// get last commit date
		repo, err := git.PlainOpen(dirname)
		if err != nil {
			return fmt.Errorf("cannot open repository %q: %w", dirname, err)
		}

		head, err := repo.Head()
		if err != nil {
			return fmt.Errorf("cannot get repository head for %q: %w", dirname, err)
		}

		c, err := repo.CommitObject(head.Hash())
		if err != nil {
			return fmt.Errorf("cannot get commit %q for repository %q: %w", head.Hash(), dirname, err)
		}
		repoDir.LastCommit = c.Author.When

		repoDirs = append(repoDirs, repoDir)
	}

	data := map[string]any{"repoDirs": repoDirs}
	contents, err := executeTemplate("index", data)
	if err != nil {
		return fmt.Errorf("cannot execute index template: %w", err)
	}

	if err := os.WriteFile("index.html", contents, 0755); err != nil {
		return fmt.Errorf("cannot write index contents to \"index.html\": %w", err)
	}

	return nil
}

func generateRepo(path string) error {
	slog.Debug("Generating repository", "path", path)

	repoInfo := &RepoInfo{Name: strings.TrimSuffix(filepath.Base(path), ".git")}

	// create and clean destination directory
	fi, err := os.Stat(repoInfo.Name)
	if err == nil && !fi.IsDir() {
		return fmt.Errorf("path %q is not a directory", repoInfo.Name)
	}
	if err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("cannot stat %q: %w", repoInfo.Name, err)
	}
	if err == nil && fi.IsDir() {
		if err := os.RemoveAll(repoInfo.Name); err != nil {
			return fmt.Errorf("cannot delete directory for %q: %w", repoInfo.Name, err)
		}
	}
	if err := os.Mkdir(repoInfo.Name, 0755); err != nil {
		return fmt.Errorf("cannot create directory for %q: %w", repoInfo.Name, err)
	}

	// read description
	description, err := readRepoFile(path, "description")
	if err != nil {
		return fmt.Errorf("cannot read description for repository %q: %w", path, err)
	}
	repoInfo.Description = description

	// read url
	url, err := readRepoFile(path, "url")
	if err != nil {
		return fmt.Errorf("cannot read url for repository %q: %w", path, err)
	}
	repoInfo.Url = url

	// open repository
	repo, err := git.PlainOpen(path)
	if err != nil {
		return fmt.Errorf("cannot open repository %q: %w", path, err)
	}

	head, err := repo.Head()
	if err != nil {
		return fmt.Errorf("cannot get repo head: %w", err)
	}

	c, err := repo.CommitObject(head.Hash())
	if err != nil {
		return fmt.Errorf("cannot get commit for hash %s: %w", head.Hash(), err)
	}

	// ToDo: populate hasReadme, hasLicense and hasContributing

	tree, err := c.Tree()
	if err != nil {
		return fmt.Errorf("cannot get tree for commit %s: %w", c, err)
	}

	slog.Debug("Processing repository tree", "head", head.Hash())
	files := []*CommitFile{}
	iErr := tree.Files().ForEach(func(o *object.File) error {
		slog.Debug("Processing tree file", "name", o.Name)

		dirpath := filepath.Join(repoInfo.Name, "file", filepath.Dir(o.Name))
		filename := filepath.Base(o.Name)
		slog.Debug("Creating directory", "dirpath", dirpath)
		if err := os.MkdirAll(dirpath, 0755); err != nil {
			return fmt.Errorf("cannot create directory %q: %w", dirpath, err)
		}

		data := map[string]any{
			"repoInfo": repoInfo,
			"filename": filename,
			"filesize": o.Size,
		}

		isBinary, err := o.IsBinary()
		if err != nil {
			return fmt.Errorf("cannot get binary state for file %q: %w", o.Name, err)
		}
		data["isBinary"] = isBinary

		if !isBinary {
			lines, err := o.Lines()
			if err != nil {
				return fmt.Errorf("cannot get lines for %q: %w", o.Name, err)
			}
			data["filelines"] = lines
		}

		contents, err := executeTemplate("file", data)
		if err != nil {
			return fmt.Errorf("cannot execute file template for file %q: %w", o.Name, err)
		}

		dstpath := filepath.Join(dirpath, fmt.Sprintf("%s.html", filename))
		if err := os.WriteFile(dstpath, contents, 0755); err != nil {
			return fmt.Errorf("cannot write file contents to %q: %w", dstpath, err)
		}

		file := &CommitFile{
			Mode: o.Mode.String(), // ToDo: correctly calculate the mode string
			Path: filepath.Join("file", fmt.Sprintf("%s.html", o.Name)),
			Name: o.Name,
		}
		files = append(files, file)

		return nil
	})
	if iErr != nil {
		return fmt.Errorf("error while processing tree: %w", iErr)
	}

	// ToDo: bundle execute and write into a function
	data := map[string]any{"repoInfo": repoInfo, "files": files}
	contents, err := executeTemplate("files", data)
	if err != nil {
		return fmt.Errorf("cannot execute files template for repository %q: %w", repoInfo.Name, err)
	}

	if err := os.WriteFile(filepath.Join(repoInfo.Name, "files.html"), contents, 0755); err != nil {
		return fmt.Errorf("cannot write files contents to \"files.html\": %w", err)
	}

	return nil
}

func main() {
	ctx := kong.Parse(&cli)
	if cli.Debug {
		slog.SetLogLoggerLevel(slog.LevelDebug)
	}

	if err := ctx.Run(); err != nil {
		fmt.Fprintf(os.Stderr, "error: %s\n", err)
		os.Exit(1)
	}
}