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
}

// ToDo: replace has* with the filename, as it can be bare or .md
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
	IsBinary bool
	Size     int64
}

type CommitInfo struct {
	Hash        string
	ParentHash  string
	Date        time.Time
	Msg         string
	AuthorName  string
	AuthorEmail string
	Files       int
	Adds        int
	Dels        int
}

//go:embed templates
var embedTmpl embed.FS
var timeShortFormatStr = "2006-01-02 15:04"
var timeLongFormatStr = time.RFC1123
var funcMap = template.FuncMap{
	"inc": func(i int) int {
		return i + 1
	},
	"menu": func(repoInfo *RepoInfo, relpath string) template.HTML {
		menu := "<a href=\"" + relpath + "log.html\">Log</a>"
		menu += " | <a href=\"" + relpath + "files.html\">Files</a>"
		menu += " | <a href=\"" + relpath + "refs.html\">Refs</a>"

		if repoInfo.HasReadme {
			menu += "| <a href=\"" + relpath + "file/README.html\">README</a>"
		}

		if repoInfo.HasLicense {
			menu += "| <a href=\"" + relpath + "file/LICENSE.html\">LICENSE</a>"
		}

		if repoInfo.HasContributing {
			menu += "| <a href=\"" + relpath + "file/CONTRIBUTING.html\">CONTRIBUTING</a>"
		}

		return template.HTML(menu)
	},
	"firstLine": func(msg string) string {
		return strings.Split(msg, "\n")[0]
	},
	"timeShortFormat": func(t time.Time) string {
		return t.Format(timeShortFormatStr)
	},
	"timeLongFormat": func(t time.Time) string {
		return t.Format(timeLongFormatStr)
	},
}

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 executeTemplateToFile(tmplName string, data any, filename string) error {
	contents, err := executeTemplate(tmplName, data)
	if err != nil {
		return fmt.Errorf("cannot execute %q template: %w", tmplName, err)
	}

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

	return 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 getRelpath(name string) string {
	return strings.Repeat("../", strings.Count(name, "/"))
}

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}
	if err := executeTemplateToFile("index", data, "index.html"); err != nil {
		return fmt.Errorf("cannot execute template %q to file %q: %w", "index", "index.html", 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.MkdirAll(filepath.Join(repoInfo.Name, "commit"), 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{
			"relpath":  getRelpath(dirpath),
			"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

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

		dstpath := filepath.Join(dirpath, fmt.Sprintf("%s.html", filename))
		if err := executeTemplateToFile("file", data, dstpath); err != nil {
			return fmt.Errorf("cannot execute template %q to file %q: %w", "file", 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,
			Lines:    len(lines),
			IsBinary: isBinary,
			Size:     o.Size,
		}
		files = append(files, file)

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

	// generate the files index file
	// ToDo: bundle execute and write into a function
	filesData := map[string]any{"repoInfo": repoInfo, "files": files, "relpath": ""}
	filesDstpath := filepath.Join(repoInfo.Name, "files.html")
	if err := executeTemplateToFile("files", filesData, filesDstpath); err != nil {
		return fmt.Errorf("cannot execute template %q to file %q: %w", "file", filesDstpath, err)
	}

	// generate the log file
	cIter, err := repo.Log(&git.LogOptions{All: true})
	if err != nil {
		return fmt.Errorf("cannot get git log for repository: %w", err)
	}

	commits := []*CommitInfo{}
	ciErr := cIter.ForEach(func(c *object.Commit) error {
		slog.Debug("Processing commit", "hash", c.Hash)

		// ToDo: is this the best way to get the number of files?
		fstats, err := c.Stats()
		if err != nil {
			return fmt.Errorf("cannot get commit stats %s: %w", c.Hash, err)
		}

		commit := &CommitInfo{
			Hash:        c.Hash.String(),
			Date:        c.Author.When, // ToDo: author when vs commiter when?
			Msg:         c.Message,
			AuthorName:  c.Author.Name,
			AuthorEmail: c.Author.Email,
			Files:       len(fstats),
		}

		if parent, _ := c.Parent(0); parent != nil {
			commit.ParentHash = parent.Hash.String()
		}

		// ToDo: are there not global commit stats?
		for _, fstat := range fstats {
			commit.Adds += fstat.Addition
			commit.Dels += fstat.Deletion
		}

		commits = append(commits, commit)

		// generate commit file
		data := map[string]any{"repoInfo": repoInfo, "commit": commit, "relpath": "../"}
		dstpath := filepath.Join(repoInfo.Name, "commit", fmt.Sprintf("%s.html", commit.Hash))
		if err := executeTemplateToFile("commit", data, dstpath); err != nil {
			return fmt.Errorf("cannot execute template %q to file %q: %w", "commit", dstpath, err)
		}

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

	logData := map[string]any{"repoInfo": repoInfo, "commits": commits, "relpath": ""}
	logDstpath := filepath.Join(repoInfo.Name, "log.html")
	if err := executeTemplateToFile("log", logData, logDstpath); err != nil {
		return fmt.Errorf("cannot execute template %q to file %q: %w", "file", logDstpath, 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)
	}
}