package api

import (
	"errors"
	"net/http"
	"time"

	"github.com/jackc/pgx/v5"

	"git.fabledsword.com/bvandeusen/minstrel/internal/apierror"
	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
	"git.fabledsword.com/bvandeusen/minstrel/internal/playlists"
)

// discoverRefreshResp is the wire shape for POST
// /api/playlists/system/discover/refresh. playlist_id is null when
// the build succeeded but the user's library yielded no eligible
// tracks (degenerate empty-library); track_count is 0 in that case.
type discoverRefreshResp struct {
	PlaylistID *string `json:"playlist_id"`
	TrackCount int32   `json:"track_count"`
}

// handleDiscoverRefresh re-runs BuildSystemPlaylists synchronously
// for the calling user, then returns the resulting Discover row's
// id + track_count. Used by the frontend's refresh affordances on
// the detail page header and the home tile kebab.
//
// Authenticated user only (gated by the authed sub-router's
// RequireUser middleware). Each user only ever refreshes their own
// Discover — no admin route, no cross-user impersonation.
func (h *handlers) handleDiscoverRefresh(w http.ResponseWriter, r *http.Request) {
	user, ok := requireUser(w, r)
	if !ok {
		return
	}
	if err := playlists.BuildSystemPlaylists(r.Context(), h.pool, h.logger, user.ID, time.Now(), h.dataDir); err != nil {
		h.logger.Error("discover refresh: build failed",
			"user_id", uuidToString(user.ID), "err", err)
		writeErr(w, apierror.InternalMsg("build failed", err))
		return
	}

	sysVariant := "discover"
	pl, err := dbq.New(h.pool).GetSystemPlaylistByVariantForUser(r.Context(),
		dbq.GetSystemPlaylistByVariantForUserParams{
			UserID:        user.ID,
			SystemVariant: &sysVariant,
		})
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			// Build succeeded but no Discover row produced — empty library.
			writeJSON(w, http.StatusOK, discoverRefreshResp{
				PlaylistID: nil, TrackCount: 0,
			})
			return
		}
		h.logger.Error("discover refresh: lookup failed",
			"user_id", uuidToString(user.ID), "err", err)
		writeErr(w, apierror.InternalMsg("lookup failed", err))
		return
	}

	idStr := uuidToString(pl.ID)
	writeJSON(w, http.StatusOK, discoverRefreshResp{
		PlaylistID: &idStr,
		TrackCount: pl.TrackCount,
	})
}