party-mix-app/apps/backend/internal/handlers/playlists.go

package handlers

import (
	"net/http"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"github.com/toyffee/party-mix/internal/models"
	"gorm.io/gorm"
)

func parseTags(s string) []string {
	if s == "" {
		return []string{}
	}
	result := []string{}
	for _, t := range strings.Split(s, ",") {
		if t = strings.TrimSpace(t); t != "" {
			result = append(result, t)
		}
	}
	return result
}

func joinTags(tags []string) string {
	cleaned := make([]string, 0, len(tags))
	for _, t := range tags {
		if t = strings.TrimSpace(t); t != "" {
			cleaned = append(cleaned, t)
		}
	}
	return strings.Join(cleaned, ",")
}

type playlistResp struct {
	models.Playlist
	Tags []string `json:"tags"`
}

type pubPlaylistResp struct {
	models.Playlist
	Tags     []string `json:"tags"`
	Username string   `json:"username"`
}

func toResp(p models.Playlist) playlistResp {
	return playlistResp{Playlist: p, Tags: parseTags(p.Tags)}
}

func GetPublicPlaylists(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		var playlists []models.Playlist
		db.Preload("Tracks", func(tx *gorm.DB) *gorm.DB {
			return tx.Order("position asc")
		}).Where("is_public = ?", true).Order("created_at desc").Find(&playlists)

		type UserRow struct {
			ID       string
			Username string
		}
		userIDs := make([]string, 0, len(playlists))
		for _, p := range playlists {
			userIDs = append(userIDs, p.UserID)
		}
		var users []UserRow
		db.Model(&models.User{}).Select("id, username").Where("id IN ?", userIDs).Find(&users)
		userMap := make(map[string]string, len(users))
		for _, u := range users {
			userMap[u.ID] = u.Username
		}

		resp := make([]pubPlaylistResp, 0, len(playlists))
		for _, p := range playlists {
			resp = append(resp, pubPlaylistResp{
				Playlist: p,
				Tags:     parseTags(p.Tags),
				Username: userMap[p.UserID],
			})
		}
		c.JSON(http.StatusOK, resp)
	}
}

func GetPlaylists(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		userID := currentUserID(c)
		var playlists []models.Playlist
		db.Preload("Tracks", func(tx *gorm.DB) *gorm.DB {
			return tx.Order("position asc")
		}).Where("user_id = ?", userID).Order("created_at desc").Find(&playlists)
		resp := make([]playlistResp, 0, len(playlists))
		for _, p := range playlists {
			resp = append(resp, toResp(p))
		}
		c.JSON(http.StatusOK, resp)
	}
}

type playlistTrackInput struct {
	Title    string `json:"title"`
	Position int    `json:"position"`
}

type playlistReq struct {
	Name     string               `json:"name" binding:"required"`
	Tracks   []playlistTrackInput `json:"tracks"`
	IsPublic bool                 `json:"is_public"`
	Tags     []string             `json:"tags"`
}

func CreatePlaylist(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		var req playlistReq
		if err := c.ShouldBindJSON(&req); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		playlist := models.Playlist{
			ID:        uuid.NewString(),
			UserID:    currentUserID(c),
			Name:      req.Name,
			IsPublic:  req.IsPublic,
			Tags:      joinTags(req.Tags),
			CreatedAt: time.Now(),
		}
		tracks := buildTracks(playlist.ID, req.Tracks)

		if err := db.Transaction(func(tx *gorm.DB) error {
			if err := tx.Create(&playlist).Error; err != nil {
				return err
			}
			if len(tracks) > 0 {
				return tx.Create(&tracks).Error
			}
			return nil
		}); err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "could not create playlist"})
			return
		}

		playlist.Tracks = tracks
		c.JSON(http.StatusCreated, toResp(playlist))
	}
}

func GetPlaylist(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		userID := currentUserID(c)
		var playlist models.Playlist
		if err := db.Preload("Tracks", func(tx *gorm.DB) *gorm.DB {
			return tx.Order("position asc")
		}).First(&playlist, "id = ?", c.Param("id")).Error; err != nil {
			c.JSON(http.StatusNotFound, gin.H{"error": "playlist not found"})
			return
		}
		if playlist.UserID != userID {
			c.JSON(http.StatusForbidden, gin.H{"error": "forbidden"})
			return
		}
		c.JSON(http.StatusOK, toResp(playlist))
	}
}

func UpdatePlaylist(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		userID := currentUserID(c)
		var playlist models.Playlist
		if err := db.First(&playlist, "id = ?", c.Param("id")).Error; err != nil {
			c.JSON(http.StatusNotFound, gin.H{"error": "playlist not found"})
			return
		}
		if playlist.UserID != userID {
			c.JSON(http.StatusForbidden, gin.H{"error": "forbidden"})
			return
		}

		var req playlistReq
		if err := c.ShouldBindJSON(&req); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		playlist.Name = req.Name
		playlist.IsPublic = req.IsPublic
		playlist.Tags = joinTags(req.Tags)
		newTracks := buildTracks(playlist.ID, req.Tracks)

		if err := db.Transaction(func(tx *gorm.DB) error {
			if err := tx.Save(&playlist).Error; err != nil {
				return err
			}
			if err := tx.Where("playlist_id = ?", playlist.ID).Delete(&models.PlaylistTrack{}).Error; err != nil {
				return err
			}
			if len(newTracks) > 0 {
				return tx.Create(&newTracks).Error
			}
			return nil
		}); err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "could not update playlist"})
			return
		}

		playlist.Tracks = newTracks
		c.JSON(http.StatusOK, toResp(playlist))
	}
}

func AddTrackToPlaylist(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		userID := currentUserID(c)
		var playlist models.Playlist
		if err := db.Preload("Tracks").First(&playlist, "id = ?", c.Param("id")).Error; err != nil {
			c.JSON(http.StatusNotFound, gin.H{"error": "playlist not found"})
			return
		}
		if playlist.UserID != userID {
			c.JSON(http.StatusForbidden, gin.H{"error": "forbidden"})
			return
		}
		var req struct {
			Title string `json:"title" binding:"required"`
		}
		if err := c.ShouldBindJSON(&req); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		track := models.PlaylistTrack{
			ID:         uuid.NewString(),
			PlaylistID: playlist.ID,
			Title:      req.Title,
			Position:   len(playlist.Tracks),
			CreatedAt:  time.Now(),
		}
		if err := db.Create(&track).Error; err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "could not add track"})
			return
		}
		c.JSON(http.StatusCreated, track)
	}
}

func DeletePlaylist(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		userID := currentUserID(c)
		var playlist models.Playlist
		if err := db.First(&playlist, "id = ?", c.Param("id")).Error; err != nil {
			c.JSON(http.StatusNotFound, gin.H{"error": "playlist not found"})
			return
		}
		if playlist.UserID != userID {
			c.JSON(http.StatusForbidden, gin.H{"error": "forbidden"})
			return
		}
		db.Where("playlist_id = ?", playlist.ID).Delete(&models.PlaylistTrack{})
		db.Delete(&playlist)
		c.Status(http.StatusNoContent)
	}
}

func buildTracks(playlistID string, inputs []playlistTrackInput) []models.PlaylistTrack {
	tracks := make([]models.PlaylistTrack, 0, len(inputs))
	for i, t := range inputs {
		if t.Title == "" {
			continue
		}
		pos := t.Position
		if pos == 0 {
			pos = i
		}
		tracks = append(tracks, models.PlaylistTrack{
			ID:         uuid.NewString(),
			PlaylistID: playlistID,
			Title:      t.Title,
			Position:   pos,
			CreatedAt:  time.Now(),
		})
	}
	return tracks
}