package handlers

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"github.com/calendarapi/internal/middleware"
	"github.com/calendarapi/internal/models"
	"github.com/calendarapi/internal/repository"
	"github.com/calendarapi/internal/service"
	"github.com/calendarapi/internal/utils"
	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
)

type ICSHandler struct {
	calSvc   *service.CalendarService
	eventSvc *service.EventService
	queries  *repository.Queries
}

func NewICSHandler(calSvc *service.CalendarService, eventSvc *service.EventService, queries *repository.Queries) *ICSHandler {
	return &ICSHandler{calSvc: calSvc, eventSvc: eventSvc, queries: queries}
}

func (h *ICSHandler) Export(w http.ResponseWriter, r *http.Request) {
	userID, _ := middleware.GetUserID(r.Context())
	calID, err := utils.ValidateUUID(chi.URLParam(r, "id"))
	if err != nil {
		utils.WriteError(w, err)
		return
	}

	if _, err := h.calSvc.GetRole(r.Context(), calID, userID); err != nil {
		utils.WriteError(w, err)
		return
	}

	now := time.Now().UTC()
	rangeStart := now.AddDate(-1, 0, 0)
	rangeEnd := now.AddDate(1, 0, 0)

	events, err := h.queries.ListEventsByCalendarInRange(r.Context(), repository.ListEventsByCalendarInRangeParams{
		CalendarID: utils.ToPgUUID(calID),
		EndTime:    utils.ToPgTimestamptz(rangeStart),
		StartTime:  utils.ToPgTimestamptz(rangeEnd),
	})
	if err != nil {
		utils.WriteError(w, models.ErrInternal)
		return
	}

	var b strings.Builder
	b.WriteString("BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//CalendarAPI//EN\r\n")

	for _, ev := range events {
		b.WriteString("BEGIN:VEVENT\r\n")
		b.WriteString(fmt.Sprintf("UID:%s\r\n", utils.FromPgUUID(ev.ID).String()))
		b.WriteString(fmt.Sprintf("DTSTART:%s\r\n", utils.FromPgTimestamptz(ev.StartTime).Format("20060102T150405Z")))
		b.WriteString(fmt.Sprintf("DTEND:%s\r\n", utils.FromPgTimestamptz(ev.EndTime).Format("20060102T150405Z")))
		b.WriteString(fmt.Sprintf("SUMMARY:%s\r\n", ev.Title))
		if ev.Description.Valid {
			b.WriteString(fmt.Sprintf("DESCRIPTION:%s\r\n", ev.Description.String))
		}
		if ev.Location.Valid {
			b.WriteString(fmt.Sprintf("LOCATION:%s\r\n", ev.Location.String))
		}
		if ev.RecurrenceRule.Valid {
			b.WriteString(fmt.Sprintf("RRULE:%s\r\n", ev.RecurrenceRule.String))
		}
		b.WriteString("END:VEVENT\r\n")
	}

	b.WriteString("END:VCALENDAR\r\n")

	w.Header().Set("Content-Type", "text/calendar")
	w.Header().Set("Content-Disposition", "attachment; filename=calendar.ics")
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(b.String()))
}

func (h *ICSHandler) Import(w http.ResponseWriter, r *http.Request) {
	userID, _ := middleware.GetUserID(r.Context())

	if err := r.ParseMultipartForm(10 << 20); err != nil {
		utils.WriteError(w, models.NewValidationError("invalid multipart form"))
		return
	}

	calIDStr := r.FormValue("calendar_id")
	calID, err := utils.ValidateUUID(calIDStr)
	if err != nil {
		utils.WriteError(w, err)
		return
	}

	role, err := h.calSvc.GetRole(r.Context(), calID, userID)
	if err != nil {
		utils.WriteError(w, err)
		return
	}
	if role != "owner" && role != "editor" {
		utils.WriteError(w, models.ErrForbidden)
		return
	}

	file, _, err := r.FormFile("file")
	if err != nil {
		utils.WriteError(w, models.NewValidationError("file required"))
		return
	}
	defer file.Close()

	data, err := io.ReadAll(file)
	if err != nil {
		utils.WriteError(w, models.ErrInternal)
		return
	}

	count := h.parseAndImportICS(r.Context(), string(data), calID, userID)

	utils.WriteJSON(w, http.StatusOK, map[string]interface{}{
		"ok":       true,
		"imported": map[string]int{"events": count},
	})
}

func (h *ICSHandler) parseAndImportICS(ctx context.Context, data string, calID, userID uuid.UUID) int {
	count := 0
	lines := strings.Split(data, "\n")
	var inEvent bool
	var title, description, location, rruleStr string
	var dtstart, dtend time.Time

	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "BEGIN:VEVENT" {
			inEvent = true
			title, description, location, rruleStr = "", "", "", ""
			dtstart, dtend = time.Time{}, time.Time{}
			continue
		}
		if line == "END:VEVENT" && inEvent {
			inEvent = false
			if title != "" && !dtstart.IsZero() && !dtend.IsZero() {
				_, err := h.queries.CreateEvent(ctx, repository.CreateEventParams{
					ID:             utils.ToPgUUID(uuid.New()),
					CalendarID:     utils.ToPgUUID(calID),
					Title:          title,
					Description:    utils.ToPgText(description),
					Location:       utils.ToPgText(location),
					StartTime:      utils.ToPgTimestamptz(dtstart),
					EndTime:        utils.ToPgTimestamptz(dtend),
					Timezone:       "UTC",
					RecurrenceRule: utils.ToPgText(rruleStr),
					Tags:           []string{},
					CreatedBy:      utils.ToPgUUID(userID),
					UpdatedBy:      utils.ToPgUUID(userID),
				})
				if err == nil {
					count++
				}
			}
			continue
		}
		if !inEvent {
			continue
		}
		switch {
		case strings.HasPrefix(line, "SUMMARY:"):
			title = strings.TrimPrefix(line, "SUMMARY:")
		case strings.HasPrefix(line, "DESCRIPTION:"):
			description = strings.TrimPrefix(line, "DESCRIPTION:")
		case strings.HasPrefix(line, "LOCATION:"):
			location = strings.TrimPrefix(line, "LOCATION:")
		case strings.HasPrefix(line, "RRULE:"):
			rruleStr = strings.TrimPrefix(line, "RRULE:")
		case strings.HasPrefix(line, "DTSTART:"):
			dtstart, _ = time.Parse("20060102T150405Z", strings.TrimPrefix(line, "DTSTART:"))
		case strings.HasPrefix(line, "DTEND:"):
			dtend, _ = time.Parse("20060102T150405Z", strings.TrimPrefix(line, "DTEND:"))
		}
	}
	return count
}