import { config } from '../config.js'
import { listDocuments, Query } from './appwriteAdmin.js'

/**
 * Abo-Stundenkonto eines Kunden.
 *
 * Gutschriften: je bezahlter Abo-Rechnung 60 min (Collection hourCredits), gueltig 12 Monate.
 * Verbrauch:    Worksheets mit countsToPlan=true auf Tickets des Kunden, je Eintrag
 *               auf 15 min aufgerundet.
 * Verrechnung:  FIFO - die aelteste noch gueltige Gutschrift wird zuerst verbraucht.
 *               Was kein Guthaben mehr findet, ist Mehraufwand (separat abzurechnen).
 * Vertragsende: Restguthaben verfaellt (siehe Abo-Bedingungen Ziff. 4).
 */

function parseSheetDate(ws) {
  const raw = ws.startDate || ws.endDate || ''
  const m = /^(\d{2})\.(\d{2})\.(\d{4})$/.exec(raw)
  if (m) return new Date(`${m[3]}-${m[2]}-${m[1]}T12:00:00Z`)
  const d = new Date(raw || ws.createdAt || ws.$createdAt)
  return Number.isNaN(d.getTime()) ? new Date(ws.$createdAt) : d
}

function roundUsage(minutes) {
  const step = config.abo.usageRoundingMinutes
  return Math.ceil(Math.max(0, Number(minutes) || 0) / step) * step
}

export async function listCredits(customerId) {
  return listDocuments(config.collections.hourCredits, [
    Query.equal('customerId', customerId),
    Query.orderAsc('grantedAt'),
    Query.limit(1000),
  ])
}

export async function listPlanUsage(customerId) {
  const workorders = await listDocuments(config.collections.workorders, [
    Query.equal('customerId', customerId),
    Query.limit(5000),
  ])
  if (!workorders.length) return []
  const byId = new Map(workorders.map((w) => [w.$id, w]))
  const ids = [...byId.keys()]
  const sheets = []
  // Appwrite begrenzt die Werte-Liste pro equal-Query -> in Bloecken abfragen
  for (let i = 0; i < ids.length; i += 100) {
    const chunk = await listDocuments(config.collections.worksheets, [
      Query.equal('workorderId', ids.slice(i, i + 100)),
      Query.equal('countsToPlan', true),
      Query.limit(5000),
    ])
    sheets.push(...chunk)
  }
  return sheets
    .filter((ws) => Number(ws.totalTime) > 0)
    .map((ws) => {
      const wo = byId.get(ws.workorderId) || {}
      return {
        id: ws.$id,
        wsid: ws.wsid || '',
        woid: ws.woid || wo.woid || '',
        topic: wo.topic || wo.title || '',
        date: parseSheetDate(ws).toISOString(),
        rawMinutes: Number(ws.totalTime) || 0,
        minutes: roundUsage(ws.totalTime),
        details: String(ws.details || '').slice(0, 300),
        employee: ws.employeeName || ws.employeeShort || '',
      }
    })
    .sort((a, b) => a.date.localeCompare(b.date))
}

/** Reine Berechnung (testbar ohne DB). */
export function computeLedger(credits, usage, { now = new Date(), active = true } = {}) {
  const pool = credits
    .map((c) => ({
      id: c.$id,
      minutes: Number(c.minutes) || 0,
      remaining: Number(c.minutes) || 0,
      grantedAt: c.grantedAt,
      expiresAt: c.expiresAt,
    }))
    .sort((a, b) => String(a.grantedAt).localeCompare(String(b.grantedAt)))

  let overageMinutes = 0
  const entries = usage.map((u) => {
    let need = u.minutes
    const at = new Date(u.date)
    for (const c of pool) {
      if (!need) break
      // Nur Gutschriften, die zum Arbeitszeitpunkt noch gueltig waren
      if (c.remaining <= 0 || new Date(c.expiresAt) <= at) continue
      const take = Math.min(need, c.remaining)
      c.remaining -= take
      need -= take
    }
    overageMinutes += need
    return { ...u, coveredMinutes: u.minutes - need, overageMinutes: need }
  })

  const valid = pool.filter((c) => c.remaining > 0 && new Date(c.expiresAt) > now)
  const expiredMinutes = pool
    .filter((c) => c.remaining > 0 && new Date(c.expiresAt) <= now)
    .reduce((s, c) => s + c.remaining, 0)
  const balanceMinutes = active ? valid.reduce((s, c) => s + c.remaining, 0) : 0
  const nextExpiry = active && valid.length
    ? valid.reduce((a, c) => (new Date(c.expiresAt) < new Date(a.expiresAt) ? c : a))
    : null

  return {
    balanceMinutes,
    grantedMinutes: pool.reduce((s, c) => s + c.minutes, 0),
    usedMinutes: entries.reduce((s, e) => s + e.coveredMinutes, 0),
    overageMinutes,
    expiredMinutes,
    nextExpiry: nextExpiry ? { minutes: nextExpiry.remaining, at: nextExpiry.expiresAt } : null,
    credits: pool.map((c) => ({
      grantedAt: c.grantedAt,
      expiresAt: c.expiresAt,
      minutes: c.minutes,
      remaining: active && new Date(c.expiresAt) > now ? c.remaining : 0,
      expired: new Date(c.expiresAt) <= now,
    })),
    usage: entries.reverse(),
  }
}

export async function getLedger(customerId, { active = true } = {}) {
  const [credits, usage] = await Promise.all([listCredits(customerId), listPlanUsage(customerId)])
  return computeLedger(credits, usage, { active })
}