package api

import (
	"net/http"
	"strconv"
	"strings"

	"reanimator/internal/repository/timeline"
)

func writeTimelineResponse(w http.ResponseWriter, r *http.Request, repo *timeline.EventRepository, subjectType string, subjectID int64) {
	limit := 50
	if raw := r.URL.Query().Get("limit"); raw != "" {
		if parsed, err := strconv.Atoi(raw); err == nil {
			limit = parsed
		} else {
			writeError(w, http.StatusBadRequest, "invalid limit")
			return
		}
	}

	var cursor *timeline.Cursor
	if raw := r.URL.Query().Get("cursor"); raw != "" {
		decoded, err := timeline.DecodeCursor(raw)
		if err != nil {
			writeError(w, http.StatusBadRequest, "invalid cursor")
			return
		}
		cursor = &decoded
	}

	items, next, err := repo.List(r.Context(), subjectType, subjectID, limit, cursor)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "list timeline failed")
		return
	}

	var nextCursor *string
	if next != nil {
		value := timeline.EncodeCursor(*next)
		nextCursor = &value
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"items":       items,
		"next_cursor": nextCursor,
	})
}

func parseTimelineID(path, prefix string) int64 {
	if !strings.HasPrefix(path, prefix) || !strings.HasSuffix(path, "/timeline") {
		return 0
	}
	trimmed := strings.TrimPrefix(path, prefix)
	trimmed = strings.TrimSuffix(trimmed, "/timeline")
	if trimmed == "" || strings.Contains(trimmed, "/") {
		return 0
	}
	id, err := strconv.ParseInt(trimmed, 10, 64)
	if err != nil || id <= 0 {
		return 0
	}
	return id
}