/**
 * Schedule-X calendar configuration factory.
 *
 * Week-start-day translation:
 *   Project convention: WEEK_START_DAY = 0  (Sunday, JS/date-fns convention)
 *   Schedule-X v4:      firstDayOfWeek = 7  (Sunday, Temporal convention)
 *
 * Passing 0 to Schedule-X silently defaults to Monday. The constant
 * WEEK_START_DAY === 0 ? 7 translation below encodes this as the source of
 * truth so the pitfall cannot recur.
 *
 * calendarId routing contract (must align with hydrateEvents.ts):
 *   Shared-family calendar → key 'shared'
 *   Per-member calendars   → key String(userId)  (NOT String(db calendarId))
 *
 * Source: https://schedule-x.dev/docs/calendar/configuration
 * Source: https://schedule-x.dev/docs/calendar/calendars
 */

import { deriveScheduleXColors } from './colorUtils.js'

/** Week start day in JS/date-fns convention: 0 = Sunday. */
export const WEEK_START_DAY = 0

/**
 * firstDayOfWeek in Schedule-X/Temporal convention: 7 = Sunday, 1 = Monday.
 *
 * Translation: WEEK_START_DAY === 0 (JS Sunday) → 7 (Temporal Sunday).
 * Hard-code to the project convention; one edit here when the user wants Monday.
 */
export const SX_FIRST_DAY_OF_WEEK: number = WEEK_START_DAY === 0 ? 7 : WEEK_START_DAY

/**
 * Per-member calendar config entry passed to buildCalendarConfig.
 *
 * id    = String(users.id)   — the Schedule-X calendars config key
 * name  = users.displayName
 * color = users.color hex
 */
export interface MemberCalendarConfig {
  id: string    // String(users.id)
  name: string  // users.displayName
  color: string // hex from users.color
}

export interface ScheduleXCalendarEntry {
  colorName: string
  lightColors: {
    main: string
    container: string
    onContainer: string
  }
}

export interface CalendarConfig {
  firstDayOfWeek: number
  calendars: Record<string, ScheduleXCalendarEntry>
}

/**
 * Build the Schedule-X calendars configuration object.
 *
 * Always includes a 'shared' entry (rose #F25C7A).
 * Adds one entry per member, keyed by String(userId).
 *
 * The keys here are the routing contract: hydrateEvents() must produce
 * calendarId values that exactly match these keys:
 *   isShared:true  → 'shared'
 *   isShared:false → String(ownerUserId)  (NOT String(db calendarId))
 */
export function buildCalendarConfig(members: MemberCalendarConfig[]): CalendarConfig {
  const calendars: Record<string, ScheduleXCalendarEntry> = {}

  // Shared-family calendar: reserved rose color, confirmed by user
  calendars['shared'] = {
    colorName: 'shared',
    lightColors: deriveScheduleXColors('#F25C7A'),
  }

  // Per-member calendars keyed by String(userId)
  for (const m of members) {
    calendars[m.id] = {
      colorName: `member-${m.id}`,
      lightColors: deriveScheduleXColors(m.color),
    }
  }

  return {
    firstDayOfWeek: SX_FIRST_DAY_OF_WEEK, // 7 = Sunday in Temporal convention
    calendars,
  }
}