package handlers

import (
	"net/http"
	"time"

	"github.com/breakpilot/school-service/internal/services"
	"github.com/gin-gonic/gin"
)

// ExportTimetableSolutionCSV streams the lessons of a solution as CSV.
// The download filename includes the solution UUID so multiple plans don't
// clobber each other when saved to disk.
func (h *Handler) ExportTimetableSolutionCSV(c *gin.Context) {
	uid := getUserID(c)
	if uid == "" {
		respondError(c, http.StatusUnauthorized, "User not authenticated")
		return
	}
	solutionID := c.Param("id")
	lessons, err := h.timetableService.LoadExportLessons(c.Request.Context(), solutionID, uid)
	if err != nil {
		respondError(c, http.StatusInternalServerError, "Failed to load lessons: "+err.Error())
		return
	}
	c.Header("Content-Type", "text/csv; charset=utf-8")
	c.Header("Content-Disposition", `attachment; filename="stundenplan-`+solutionID+`.csv"`)
	c.Writer.WriteHeader(http.StatusOK)
	if err := services.WriteCSV(c.Writer, lessons); err != nil {
		// Best-effort; headers already flushed.
		_ = c.Writer.Flush
	}
}

// ExportTimetableSolutionICS emits a single-week iCalendar. The reference
// Monday defaults to the next Monday from "now"; callers can override via
// ?start=YYYY-MM-DD to align to a school year.
func (h *Handler) ExportTimetableSolutionICS(c *gin.Context) {
	uid := getUserID(c)
	if uid == "" {
		respondError(c, http.StatusUnauthorized, "User not authenticated")
		return
	}
	solutionID := c.Param("id")

	weekStart := services.NextMonday(time.Now())
	if param := c.Query("start"); param != "" {
		parsed, err := time.Parse("2006-01-02", param)
		if err != nil {
			respondError(c, http.StatusBadRequest, "start must be YYYY-MM-DD")
			return
		}
		weekStart = parsed
	}

	sol, err := h.timetableService.GetSolution(c.Request.Context(), solutionID, uid)
	if err != nil {
		respondError(c, http.StatusNotFound, "Solution not found")
		return
	}
	lessons, err := h.timetableService.LoadExportLessons(c.Request.Context(), solutionID, uid)
	if err != nil {
		respondError(c, http.StatusInternalServerError, "Failed to load lessons: "+err.Error())
		return
	}

	c.Header("Content-Type", "text/calendar; charset=utf-8")
	c.Header("Content-Disposition", `attachment; filename="stundenplan-`+solutionID+`.ics"`)
	c.Writer.WriteHeader(http.StatusOK)
	if err := services.WriteICS(c.Writer, lessons, weekStart, sol.Name); err != nil {
		// Same best-effort situation as CSV.
		_ = c.Writer.Flush
	}
}