package content

import (
	"bytes"
	"context"
	"io"
	"io/fs"
	"os"
	"path"
	"path/filepath"
	"slices"
	"strings"
	"time"

	"go.alanpearce.eu/homestead/internal/markdown"
	"go.alanpearce.eu/homestead/internal/vcs"
	"go.alanpearce.eu/x/log"

	"github.com/adrg/frontmatter"
	mapset "github.com/deckarep/golang-set/v2"
	"gitlab.com/tozd/go/errors"
)

var SkipList = []string{
	"LICENSE",
	"taplo.toml",
}

type PostMatter struct {
	Date        time.Time
	Description string
	Title       string
	Taxonomies  struct {
		Tags []string
	}
}

type Post struct {
	Input    string
	Basename string
	URL      string
	Commits  []*vcs.Commit
	*PostMatter

	content []byte
}

type Config struct {
	Root    string
	PostDir string
	Repo    *vcs.Repository
}

type Collection struct {
	config *Config
	log    *log.Logger

	Posts       []*Post
	Pages       []*Post
	StaticFiles []string
	Tags        mapset.Set[string]
}

var postURLReplacer = strings.NewReplacer(
	"index.md", "",
	".md", "/",
)

func (cc *Collection) GetPost(filename string) (*Post, error) {
	fp := filepath.Join(cc.config.Root, filename)
	url := path.Join("/", postURLReplacer.Replace(filename)) + "/"
	cs, err := cc.config.Repo.GetFileLog(filename)
	if err != nil {
		return nil, errors.WithMessagef(err, "could not get commit log for file %s", filename)
	}
	post := &Post{
		Input:      filename,
		Basename:   filepath.Base(url),
		URL:        url,
		PostMatter: &PostMatter{},
		Commits:    cs,
	}

	err = parse(fp, post)
	if err != nil {
		return nil, err
	}

	return post, nil
}

var pageURLReplacer = strings.NewReplacer(
	"index.md", "",
	".md", "",
)

func (cc *Collection) GetPage(filename string) (*Post, error) {
	fp := filepath.Join(cc.config.Root, filename)
	url := path.Join("/", pageURLReplacer.Replace(filename))
	cs, err := cc.config.Repo.GetFileLog(filename)
	if err != nil {
		return nil, errors.WithMessagef(err, "could not get commit log for file %s", filename)
	}
	post := &Post{
		Input:      filename,
		Basename:   filepath.Base(url),
		URL:        url,
		PostMatter: &PostMatter{},
		Commits:    cs,
	}

	err = parse(fp, post)
	if err != nil {
		return nil, err
	}

	if post.Date.IsZero() && len(cs) > 1 {
		post.Date = cs[0].Date
	}

	return post, nil
}

func parse(fp string, post *Post) error {
	content, err := os.Open(fp)
	if err != nil {
		return errors.WithMessagef(err, "could not open post %s", fp)
	}
	defer content.Close()

	post.content, err = frontmatter.Parse(content, post.PostMatter)
	if err != nil {
		return errors.WithMessagef(
			err,
			"could not parse front matter of post %s",
			fp,
		)
	}

	return nil
}

// implements templ.Component
func (p *Post) Render(_ context.Context, w io.Writer) error {
	return markdown.Convert(p.content, w)
}

func (p *Post) RenderString() (string, error) {
	var buf bytes.Buffer
	if err := p.Render(context.Background(), &buf); err != nil {
		return "", errors.WithMessage(err, "could not convert markdown content")
	}

	return buf.String(), nil
}

func (cc *Collection) HandleFile(filename string, d fs.DirEntry) error {
	switch {
	case strings.HasPrefix(filename, ".") &&
		filename != "." &&
		!strings.HasPrefix(filename, ".well-known"):

		cc.log.Debug("skipping", "filename", filename, "is_dir", d.Type().IsDir())
		if d.Type().IsDir() {
			return fs.SkipDir
		}
	case !d.Type().IsDir():
		if filepath.Ext(filename) == ".md" {
			if strings.HasPrefix(filename, cc.config.PostDir) {
				post, err := cc.GetPost(filename)
				if err != nil {
					return err
				}

				for _, tag := range post.PostMatter.Taxonomies.Tags {
					cc.Tags.Add(strings.ToLower(tag))
				}
				cc.Posts = append(cc.Posts, post)
			} else {
				page, err := cc.GetPage(filename)
				if err != nil {
					return err
				}
				cc.Pages = append(cc.Pages, page)
			}
		} else if !slices.Contains(SkipList, filename) {
			cc.StaticFiles = append(cc.StaticFiles, filename)
		}
	}

	return nil
}

func NewContentCollection(config *Config, log *log.Logger) (*Collection, error) {
	cc := &Collection{
		Posts:       []*Post{},
		Tags:        mapset.NewSet[string](),
		Pages:       []*Post{},
		StaticFiles: []string{},
		config:      config,
		log:         log,
	}

	err := filepath.WalkDir(config.Root, func(filename string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		filename, err = filepath.Rel(config.Root, filename)
		if err != nil {
			return err
		}

		log.Debug("walking", "filename", filename)

		return cc.HandleFile(filename, d)
	})

	slices.SortFunc(cc.Posts, func(a, b *Post) int {
		return b.Date.Compare(a.Date)
	})

	if err != nil {
		return nil, errors.WithMessage(err, "could not walk directory")
	}

	return cc, nil
}