package main

import (
	"net/http"
	"strconv"

	"github.com/x0gp/server/internal/races"
	"github.com/x0gp/server/internal/transport"
)

// leaderboardHandler godoc
// @Summary      Leaderboard
// @Description  Returns paginated leaderboard list. Supports overall leaderboard or track-specific leaderboard for the current year.
// @Tags         leaderboard
// @Produce      json
// @Param        track_id     query string false "Track ID. If empty, returns overall leaderboard."
// @Param        year         query int    false "Year. Defaults to current year."
// @Param        limit        query int    false "Limit (1..200, default 50)"
// @Param        offset       query int    false "Offset (default 0)"
// @Param        X-Driver-Id  header string false "Current driver ID. Defaults to driver-seed-001 (mock Alice)."
// @Success      200 {object} transport.LeaderboardResponse "Leaderboard page and current driver position"
// @Failure      400 {object} map[string]interface{}        "Invalid input"
// @Failure      500 {object} map[string]interface{}        "Internal server error"
// @Router       /api/leaderboard [get]
func leaderboardHandler(svc *races.Service) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		trackID := r.URL.Query().Get("track_id")

		yearVal := r.URL.Query().Get("year")
		var year int
		if yearVal != "" {
			var err error
			year, err = strconv.Atoi(yearVal)
			if err != nil {
				writeError(w, http.StatusBadRequest, "invalid_input", "invalid year")
				return
			}
		}

		limit := 50
		limitVal := r.URL.Query().Get("limit")
		if limitVal != "" {
			var err error
			limit, err = strconv.Atoi(limitVal)
			if err != nil || limit <= 0 {
				writeError(w, http.StatusBadRequest, "invalid_input", "invalid limit")
				return
			}
			if limit > 200 {
				limit = 200
			}
		}

		offset := 0
		offsetVal := r.URL.Query().Get("offset")
		if offsetVal != "" {
			var err error
			offset, err = strconv.Atoi(offsetVal)
			if err != nil || offset < 0 {
				writeError(w, http.StatusBadRequest, "invalid_input", "invalid offset")
				return
			}
		}

		driverID := r.Header.Get("X-Driver-Id")
		if driverID == "" {
			driverID = "driver-seed-001" // mock current driver
		}

		res, err := svc.GetLeaderboard(r.Context(), trackID, year, limit, offset, driverID)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "internal", err.Error())
			return
		}

		items := make([]transport.LeaderboardEntry, 0, len(res.Items))
		for _, item := range res.Items {
			items = append(items, leaderboardEntryToWire(item))
		}

		var curDriver *transport.LeaderboardEntry
		if res.CurrentDriver != nil {
			wire := leaderboardEntryToWire(*res.CurrentDriver)
			curDriver = &wire
		}

		writeJSON(w, http.StatusOK, transport.LeaderboardResponse{
			Items:         items,
			Total:         res.Total,
			Limit:         limit,
			Offset:        offset,
			CurrentDriver: curDriver,
		})
	}
}

func leaderboardEntryToWire(e races.LeaderboardEntry) transport.LeaderboardEntry {
	var bestPos *int
	if e.BestPos != nil {
		pos := *e.BestPos
		bestPos = &pos
	}
	var bestTime *int64
	if e.BestTimeMs != nil {
		val := *e.BestTimeMs
		bestTime = &val
	}
	return transport.LeaderboardEntry{
		DriverID:   e.DriverID,
		Nickname:   e.Nickname,
		Name:       e.Name,
		AvatarURL:  e.AvatarURL,
		ClanID:     e.ClanID,
		ClanTag:    e.ClanTag,
		Points:     e.Points,
		BestPos:    bestPos,
		BestTimeMs: bestTime,
		Rank:       e.Rank,
	}
}