package builder

import (
	"context"
	"fmt"
	"io"
	"os"
	"path"
	"path/filepath"
	"slices"
	"time"

	"go.alanpearce.eu/homestead/internal/buffer"
	"go.alanpearce.eu/homestead/internal/builder/template"
	"go.alanpearce.eu/homestead/internal/config"
	"go.alanpearce.eu/homestead/internal/content"
	"go.alanpearce.eu/homestead/internal/sitemap"
	"go.alanpearce.eu/homestead/internal/storage"
	"go.alanpearce.eu/homestead/internal/vcs"
	"go.alanpearce.eu/homestead/templates"
	"go.alanpearce.eu/x/log"

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

type Options struct {
	Source       string     `conf:"default:.,short:s,flag:src"`
	Development  bool       `conf:"default:false,flag:dev"`
	VCSRemoteURL config.URL `conf:"default:https://git.alanpearce.eu/website"`

	Storage storage.Writer  `conf:"-"`
	Repo    *vcs.Repository `conf:"-"`
}

func joinSourcePath(src string) func(string) string {
	return func(rel string) string {
		return filepath.Join(src, rel)
	}
}

func copyFile(storage storage.Writer, src string, rel string) error {
	buf := new(buffer.Buffer)

	sf, err := os.Open(src)
	if err != nil {
		return err
	}
	defer sf.Close()
	buf.Reset()
	if _, err := io.Copy(buf, sf); err != nil {
		return err
	}
	if err := storage.Write("/"+rel, "", buf); err != nil {
		return err
	}

	return nil
}

func build(
	options *Options,
	config *config.Config,
	log *log.Logger,
) error {
	ctx := context.TODO()
	buf := new(buffer.Buffer)
	joinSource := joinSourcePath(options.Source)
	storage := options.Storage

	log.Debug("reading posts", "source", options.Source)
	cc, err := content.NewContentCollection(&content.Config{
		Root:    options.Source,
		PostDir: "post",
		Repo:    options.Repo,
	}, log.Named("content"))
	if err != nil {
		return err
	}

	sitemap := sitemap.New(config)
	lastMod := time.Now()
	if len(cc.Posts) > 0 {
		lastMod = cc.Posts[0].Date
	}

	for _, post := range cc.Posts {
		log.Debug("rendering post", "post", post.Basename)
		sitemap.AddPath(post.URL, post.Date)
		buf.Reset()
		if err := templates.PostPage(config, post).Render(ctx, buf); err != nil {
			return errors.WithMessage(err, "could not render post")
		}

		if err := storage.WritePost(post, buf); err != nil {
			return err
		}
	}

	log.Debug("rendering tags list")
	buf.Reset()
	if err := templates.TagsPage(config, "tags", mapset.Sorted(cc.Tags), "/tags").Render(ctx, buf); err != nil {
		return err
	}
	if err := storage.Write("/tags/", "Tags", buf); err != nil {
		return err
	}
	sitemap.AddPath("/tags/", lastMod)

	for _, tag := range cc.Tags.ToSlice() {
		matchingPosts := []*content.Post{}
		for _, post := range cc.Posts {
			if slices.Contains(post.Taxonomies.Tags, tag) {
				matchingPosts = append(matchingPosts, post)
			}
		}
		log.Debug("rendering tags page", "tag", tag)
		url := path.Join("/tags", tag) + "/"
		buf.Reset()
		if err := templates.TagPage(config, tag, matchingPosts, url).Render(ctx, buf); err != nil {
			return err
		}
		if err = storage.Write(url, tag, buf); err != nil {
			return err
		}
		sitemap.AddPath(url, matchingPosts[0].Date)

		log.Debug("rendering tags feed", "tag", tag)
		title := fmt.Sprintf("%s - %s", config.Title, tag)
		feed, err := template.RenderFeed(
			title,
			config,
			matchingPosts,
			tag,
		)
		if err != nil {
			return errors.WithMessage(err, "could not render tag feed page")
		}
		buf.Reset()
		if _, err := feed.WriteTo(buf); err != nil {
			return err
		}
		if err := storage.Write(path.Join("/tags", tag, "atom.xml"), title, buf); err != nil {
			return err
		}
	}

	log.Debug("rendering list page")
	buf.Reset()
	if err := templates.ListPage(config, cc.Posts, "/post").Render(ctx, buf); err != nil {
		return err
	}
	if err := storage.Write("/post/", "Posts", buf); err != nil {
		return err
	}
	sitemap.AddPath("/post/", lastMod)

	log.Debug("rendering feed")
	feed, err := template.RenderFeed(config.Title, config, cc.Posts, "feed")
	if err != nil {
		return errors.WithMessage(err, "could not render feed")
	}
	buf.Reset()
	if _, err := feed.WriteTo(buf); err != nil {
		return err
	}
	if err := storage.Write("/atom.xml", config.Title, buf); err != nil {
		return err
	}

	for _, filename := range []string{"feed-styles.xsl", "style.css"} {
		buf.Reset()
		log.Debug("rendering template file", "filename", filename)
		if err := template.CopyFile(filename, buf); err != nil {
			return errors.WithMessagef(err, "could not render template file %s", filename)
		}
		if err := storage.Write("/"+filename, "", buf); err != nil {
			return err
		}
	}

	for _, post := range cc.Pages {
		buf.Reset()
		log.Debug("rendering page", "source", post.Input, "path", post.URL)
		if post.URL == "/" {
			if err := templates.Homepage(config, cc.Posts, post).Render(ctx, buf); err != nil {
				return err
			}
		} else {
			if err := templates.Page(config, post).Render(ctx, buf); err != nil {
				return err
			}
		}
		file := storage.NewFileFromPost(post)
		file.ContentType = "text/html; charset=utf-8"
		if err := storage.WriteFile(file, buf); err != nil {
			return err
		}
	}

	// it would be nice to set LastMod here, but using the latest post
	// date would be wrong as the homepage has its own content file
	// without a date, which could be newer
	sitemap.AddPath("/", time.Time{})
	err = buf.SeekStart()
	if err != nil {
		return err
	}

	log.Debug("rendering sitemap")
	buf.Reset()
	if _, err := sitemap.WriteTo(buf); err != nil {
		return err
	}
	if err := storage.Write("/sitemap.xml", "sitemap", buf); err != nil {
		return err
	}

	log.Debug("rendering robots.txt")
	rob, err := template.RenderRobotsTXT(config)
	if err != nil {
		return err
	}
	buf.Reset()
	if _, err := io.Copy(buf, rob); err != nil {
		return err
	}
	if err := storage.Write("/robots.txt", "", buf); err != nil {
		return err
	}

	for _, sf := range cc.StaticFiles {
		src := joinSource(sf)
		log.Debug("copying static file", "sf", sf, "src", src)
		err = copyFile(storage, src, sf)
		if err != nil {
			return err
		}
	}

	return nil
}

func BuildSite(options *Options, cfg *config.Config, log *log.Logger) error {
	if cfg == nil {
		return errors.New("config is nil")
	}
	cfg.InjectLiveReload = options.Development

	templates.Init()

	return build(options, cfg, log)
}