package handlers

import (
	"context"
	"net/http"
	"strings"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

type postAttachmentDownloadInfo struct {
	URL      string
	Filename string
	Mime     string
}

func loadPublishedPostAttachment(ctx context.Context, pool *pgxpool.Pool, postID, aid uuid.UUID) (postAttachmentDownloadInfo, error) {
	var info postAttachmentDownloadInfo
	err := pool.QueryRow(ctx, `
		SELECT pa.url, COALESCE(NULLIF(TRIM(pa.filename), ''), 'download'), COALESCE(NULLIF(TRIM(pa.mime), ''), 'application/octet-stream')
		FROM post_attachments pa
		JOIN posts p ON p.id = pa.post_id
		WHERE pa.id = $1 AND pa.post_id = $2
			AND `+publicPostWhere, aid, postID,
	).Scan(&info.URL, &info.Filename, &info.Mime)
	if err != nil {
		return info, err
	}
	info.URL = strings.TrimSpace(info.URL)
	if info.URL == "" {
		return info, pgx.ErrNoRows
	}
	return info, nil
}

func incrPostDownloadCount(ctx context.Context, pool *pgxpool.Pool, postID uuid.UUID) error {
	cmd, err := pool.Exec(ctx, `
		UPDATE posts SET download_count = download_count + 1, updated_at = NOW()
		WHERE id = $1 AND `+publicPostWhere, postID)
	if err != nil {
		return err
	}
	if cmd.RowsAffected() == 0 {
		return pgx.ErrNoRows
	}
	return nil
}

func handlePostAttachmentDownload(w http.ResponseWriter, r *http.Request, redirect bool) {
	pool := poolFrom(r)
	postID, err := uuid.Parse(chi.URLParam(r, "id"))
	if err != nil {
		http.Error(w, "bad id", http.StatusBadRequest)
		return
	}
	aid, err := uuid.Parse(chi.URLParam(r, "aid"))
	if err != nil {
		http.Error(w, "bad attachment id", http.StatusBadRequest)
		return
	}
	ctx := r.Context()
	info, err := loadPublishedPostAttachment(ctx, pool, postID, aid)
	if err != nil {
		if err == pgx.ErrNoRows {
			http.NotFound(w, r)
			return
		}
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if err := incrPostDownloadCount(ctx, pool, postID); err != nil {
		if err == pgx.ErrNoRows {
			http.NotFound(w, r)
			return
		}
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if redirect {
		http.Redirect(w, r, info.URL, http.StatusFound)
		return
	}
	writeJSON(w, map[string]any{
		"ok":       true,
		"url":      info.URL,
		"filename": info.Filename,
		"mime":     info.Mime,
	})
}

// PostAttachmentDownload increments download_count and returns the attachment file URL for the client to open/save.
func PostAttachmentDownload(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	handlePostAttachmentDownload(w, r, false)
}

// GetPostAttachmentDownload increments download_count and redirects the browser to the attachment URL.
func GetPostAttachmentDownload(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	handlePostAttachmentDownload(w, r, true)
}