package handlers

import (
	"net/http"
	"time"

	"github.com/gin-contrib/sessions"
	"github.com/gin-gonic/gin"
	"go_blog/models"

	"gorm.io/gorm"
)

// publishedArticleOrder is the ordering used to list published articles:
// pinned first, then by most recent publish/creation time.
const publishedArticleOrder = "is_top DESC, published_at DESC, created_at DESC"

// HomePage renders the public home page with the latest published articles.
func HomePage(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		tr := getTr(c)
		data := DefaultData(c)
		data["Title"] = tr["page_home"]

		var articles []models.Article
		db.Where("status = ?", models.ArticlePublished).
			Order(publishedArticleOrder).
			Limit(10).
			Find(&articles)
		data["Articles"] = articles

		c.HTML(http.StatusOK, "home", data)
	}
}

// ArticleDetail renders a single published article by its slug.
func ArticleDetail(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		tr := getTr(c)
		slug := c.Param("slug")

		var article models.Article
		err := db.Where("slug = ? AND status = ?", slug, models.ArticlePublished).
			Preload("Author").
			First(&article).Error
		if err != nil {
			data := DefaultData(c)
			data["Title"] = tr["article_not_found"]
			c.HTML(http.StatusNotFound, "article_not_found", data)
			return
		}

		// Increment view count; ignore errors so a view never breaks the page.
		db.Model(&models.Article{}).Where("id = ?", article.ID).
			UpdateColumn("view_count", gorm.Expr("view_count + 1"))

		// One-time flash notice (set by PostComment on success/pending). Reading
		// consumes the flash, so refreshing the page no longer re-shows it.
		notice := readCommentFlash(c)
		renderArticleDetail(c, db, &article, commentForm{}, "", notice)
	}
}

// renderArticleDetail renders the article page, including the comment section.
// formErr refills the form with an error banner; notice is a one-time
// success/pending banner (already consumed from the session by the caller).
func renderArticleDetail(c *gin.Context, db *gorm.DB, article *models.Article, form commentForm, formErr, notice string) {
	tr := getTr(c)

	authorName := article.Author.Username
	if article.Author.DisplayName != "" {
		authorName = article.Author.DisplayName
	}

	viewer := viewerFromContext(c)

	var comments []models.Comment
	db.Where("article_id = ?", article.ID).Order("created_at ASC").Find(&comments)
	cfg := models.GetCommentConfig()
	useGravatar := cfg != nil && cfg.UseGravatar
	tree := buildCommentTree(comments, viewer, tr, useGravatar)

	data := DefaultData(c)
	data["Title"] = article.Title
	data["Article"] = article
	data["AuthorName"] = authorName
	data["PublishedAt"] = formatPublishTime(article.PublishedAt)
	data["Comments"] = tree
	data["CommentConfig"] = models.GetCommentConfig()
	data["CommentForm"] = form
	data["CommentError"] = formErr
	data["CommentNotice"] = notice
	data["MaxCommentLength"] = MaxCommentLength
	c.HTML(http.StatusOK, "article", data)
}

// formatPublishTime returns the publication time as a readable string, falling
// back to the creation time when the publish timestamp is unset.
func formatPublishTime(publishedAt *time.Time) string {
	if publishedAt != nil {
		return publishedAt.Format("2006-01-02 15:04")
	}
	return ""
}

// commentFlashKey is the session key for the one-time comment notice.
const commentFlashKey = "comment_flash"

// setCommentFlash stores a one-time comment notice in the session so the
// following GET /article/:slug (after the POST/redirect) can show it once and
// never again on refresh.
func setCommentFlash(c *gin.Context, value string) {
	session := sessions.Default(c)
	session.Set(commentFlashKey, value)
	session.Save()
}

// readCommentFlash returns and clears the one-time comment notice, if any.
func readCommentFlash(c *gin.Context) string {
	session := sessions.Default(c)
	v, ok := session.Get(commentFlashKey).(string)
	if ok && v != "" {
		session.Delete(commentFlashKey)
		session.Save()
		return v
	}
	return ""
}