package http

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"html/template"
	"net/http"
	"path/filepath"
	"strings"
	"time"

	"dev.mediocregopher.com/mediocre-blog.git/src/http/apiutil"
	"dev.mediocregopher.com/mediocre-blog.git/src/post"
	"dev.mediocregopher.com/mediocre-blog.git/src/post/asset"
	"dev.mediocregopher.com/mediocre-blog.git/src/render"
	"dev.mediocregopher.com/mediocre-go-lib.git/mctx"
)

type postPreprocessFuncs struct {
	urlBuilder render.URLBuilder
	imageTpl   *template.Template
}

func newPostPreprocessFuncs(urlBuilder render.URLBuilder) postPreprocessFuncs {
	imageTpl := template.New("image.html")
	imageTpl = template.Must(imageTpl.Parse(mustReadTplFile("image.html")))
	return postPreprocessFuncs{urlBuilder, imageTpl}
}

func (f postPreprocessFuncs) Image(args ...string) (string, error) {

	var (
		id    = args[0]
		descr = "TODO"
	)

	if len(args) > 1 {
		descr = args[1]
	}

	var (
		tplPayload = struct {
			RootURL   render.URLBuilder
			ID        string
			Descr     string
			Resizable bool
		}{
			RootURL:   f.urlBuilder,
			ID:        id,
			Descr:     descr,
			Resizable: asset.IsImageResizable(id),
		}
		buf = new(bytes.Buffer)
	)

	err := f.imageTpl.ExecuteTemplate(buf, "image.html", tplPayload)
	if err != nil {
		return "", err
	}

	return buf.String(), nil
}

func (a *api) getPostsHandler() http.Handler {
	var (
		tpl            = a.mustParseBasedTpl("posts.html")
		getPostHandler = a.getPostHandler()
	)

	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		if id := filepath.Base(r.URL.Path); id != "/" {
			getPostHandler.ServeHTTP(rw, r)
			return
		}
		a.executeTemplate(rw, r, tpl, nil)
	})
}

func (a *api) getPostHandler() http.Handler {

	tpl := a.mustParseBasedTpl("post.html")

	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		a.executeTemplate(rw, r, tpl, nil)
	})
}

func (a *api) managePostsHandler() http.Handler {
	tpl := a.mustParseBasedTpl("posts-manage.html")
	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		a.executeTemplate(rw, r, tpl, nil)
	})
}

func (a *api) editPostHandler(isDraft bool) http.Handler {
	tpl := a.mustParseBasedTpl("post-edit.html")
	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		a.executeTemplate(rw, r, tpl, struct {
			IsDraft bool
			Formats []post.Format
		}{
			IsDraft: isDraft,
			Formats: post.Formats,
		})
	})
}

func postFromPostReq(r *http.Request) (post.Post, error) {

	formatStr := r.PostFormValue("format")
	if formatStr == "" {
		return post.Post{}, errors.New("format is required")
	}

	format, err := post.FormatFromString(formatStr)
	if err != nil {
		return post.Post{}, fmt.Errorf("parsing format: %w", err)
	}

	p := post.Post{
		ID:          r.PostFormValue("id"),
		Title:       r.PostFormValue("title"),
		Description: r.PostFormValue("description"),
		Tags:        strings.Fields(r.PostFormValue("tags")),
		Series:      r.PostFormValue("series"),
		Format:      format,
	}

	// textareas encode newlines as CRLF for historical reasons
	p.Body = r.PostFormValue("body")
	p.Body = strings.ReplaceAll(p.Body, "\r\n", "\n")
	p.Body = strings.TrimSpace(p.Body)

	if p.ID == "" ||
		p.Title == "" ||
		p.Body == "" ||
		len(p.Tags) == 0 {
		return post.Post{}, errors.New("id, ritle, tags, and body are all required")
	}

	return p, nil
}

func (a *api) publishPost(ctx context.Context, p post.Post) error {

	first, err := a.params.PostStore.Set(p, time.Now())

	if err != nil {
		return fmt.Errorf("storing post with id %q: %w", p.ID, err)
	}

	if !first {
		return nil
	}

	if err := a.params.PostDraftStore.Delete(p.ID); err != nil {
		return fmt.Errorf("deleting draft: %w", err)
	}

	return nil
}

func (a *api) postPostHandler() http.Handler {

	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		var (
			ctx    = r.Context()
			logger = a.params.Logger
		)

		p, err := postFromPostReq(r)
		if err != nil {
			apiutil.BadRequest(ctx, logger, rw, "%w", err)
			return
		}

		ctx = mctx.Annotate(ctx, "postID", p.ID)

		if err := a.publishPost(ctx, p); err != nil {
			apiutil.InternalServerError(
				ctx, logger, rw, "publishing post with id %q: %w", p.ID, err,
			)
			return
		}

		a.executeRedirectTpl(
			rw, r, a.urlBuilder.Post(p.ID).MethodEdit().String(),
		)
	})
}

func (a *api) deletePostHandler(isDraft bool) http.Handler {

	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		var (
			ctx    = r.Context()
			logger = a.params.Logger
			id     = filepath.Base(r.URL.Path)
		)

		if id == "/" {
			apiutil.BadRequest(ctx, logger, rw, "id is required")
			return
		}

		var err error

		if isDraft {
			err = a.params.PostDraftStore.Delete(id)
		} else {
			err = a.params.PostStore.Delete(id)
		}

		if errors.Is(err, post.ErrPostNotFound) {
			http.Error(rw, "Post not found", 404)
			return
		} else if err != nil {
			apiutil.InternalServerError(
				ctx, logger, rw, "deleting post with id %q: %w", id, err,
			)
			return
		}

		if isDraft {
			a.executeRedirectTpl(
				rw, r, a.urlBuilder.Drafts().MethodManage().String(),
			)
		} else {
			a.executeRedirectTpl(
				rw, r, a.urlBuilder.Posts().MethodManage().String(),
			)
		}
	})
}

func (a *api) previewPostHandler() http.Handler {

	tpl := a.mustParseBasedTpl("post.html")

	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
		var (
			ctx    = r.Context()
			logger = a.params.Logger
		)

		p, err := postFromPostReq(r)
		if err != nil {
			apiutil.BadRequest(ctx, logger, rw, "%w", err)
			return
		}

		storedPost := post.StoredPost{
			Post:        p,
			PublishedAt: time.Now(),
		}

		r = r.WithContext(render.WithPost(ctx, storedPost))
		a.executeTemplate(rw, r, tpl, nil)
	})
}