package blog

import (
	"net/http"
	"strconv"
	"time"

	"git.golem15.com/golem15/summercms/docs/examples/blog/models"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/wire"
	"gorm.io/gorm"
)

var _ pact.HasRoutes = (*Plugin)(nil)

// Routes replaces routes.php.
func (p *Plugin) Routes(r pact.Router) error {
	r.Get("/api/blog/posts", p.listPosts)
	return nil
}

// postJSON is the response shape of one post. It is built field by field,
// so a column added to the model never leaks into the API.
type postJSON struct {
	ID          uint      `json:"id"`
	Title       string    `json:"title"`
	Slug        string    `json:"slug"`
	Body        string    `json:"body"`
	PublishedAt wire.Time `json:"published_at"`
}

// listPosts answers GET /api/blog/posts?page=N&per_page=M with one page of
// published posts, newest first, in the {data, meta} shape of Laravel's
// paginator. Drafts, whose published_at is NULL, are never listed.
func (p *Plugin) listPosts(w http.ResponseWriter, r *http.Request) {
	db, ok := p.app.Lookup[*gorm.DB]()
	if !ok {
		wire.WriteJSON(w, http.StatusServiceUnavailable, map[string]string{"message": "database unavailable"})
		return
	}
	page := queryInt(r, "page", 1, 1, 10000)
	perPage := queryInt(r, "per_page", p.app.Config.Int("acme.blog.per_page"), 1, 100)

	q := db.WithContext(r.Context()).Model(&models.Post{}).Where("published_at IS NOT NULL")
	var total int64
	if err := q.Count(&total).Error; err != nil {
		wire.WriteOpaque500(w)
		return
	}
	var posts []models.Post
	if err := q.Order("published_at DESC, id DESC").Offset((page - 1) * perPage).Limit(perPage).Find(&posts).Error; err != nil {
		wire.WriteOpaque500(w)
		return
	}
	rows := make([]postJSON, 0, len(posts))
	for _, post := range posts {
		rows = append(rows, postJSON{
			ID:          post.ID,
			Title:       post.Title,
			Slug:        post.Slug,
			Body:        post.Body,
			PublishedAt: wire.Time{Time: post.PublishedAt.UTC().Truncate(time.Second)},
		})
	}
	wire.WriteJSON(w, http.StatusOK, lagoon.Paginate(rows, page, perPage, total))
}

// queryInt reads an integer query parameter, falling back to def when it is
// missing or not a number, and clamps it to [lo, hi].
func queryInt(r *http.Request, name string, def, lo, hi int) int {
	n, err := strconv.Atoi(r.URL.Query().Get(name))
	if err != nil {
		n = def
	}
	return min(max(n, lo), hi)
}