import { uuidv7 } from '@sims/domain'
import { ownerScope } from './auth'
import { writeAudit } from './audit'
import type { DB } from './db'
import {
  QUOTE_FOLLOWUP_DEFAULT_BODY, QUOTE_FOLLOWUP_DEFAULT_SUBJECT, type ReminderRuleKind,
} from './reminder-templates'

/** Reminder rows + settings helpers (D12 plain-repo pattern). The UNIQUE key
 *  (rule_kind, subject_id, due_period) is the whole idempotency story — every
 *  create goes through INSERT … ON CONFLICT DO NOTHING, so catch-up after downtime is safe. */

export type ReminderStatus = 'queued' | 'sent' | 'failed' | 'dismissed'

export interface Reminder {
  id: string; ruleKind: ReminderRuleKind; subjectId: string; duePeriod: string
  clientId: string; docId: string | null; status: ReminderStatus
  policyApplied: 'auto' | 'manual'; error: string | null; createdAt: string; sentAt: string | null
}

interface ReminderRow {
  id: string; rule_kind: string; subject_id: string; due_period: string; client_id: string
  doc_id: string | null; status: string; policy_applied: string; error: string | null
  created_at: string; sent_at: string | null
}

function toReminder(r: ReminderRow): Reminder {
  return {
    id: r.id, ruleKind: r.rule_kind as ReminderRuleKind, subjectId: r.subject_id,
    duePeriod: r.due_period, clientId: r.client_id, docId: r.doc_id,
    status: r.status as ReminderStatus, policyApplied: r.policy_applied as 'auto' | 'manual',
    error: r.error, createdAt: r.created_at, sentAt: r.sent_at,
  }
}

export async function getReminder(db: DB, id: string): Promise<Reminder | null> {
  const row = await db.get<ReminderRow>(`SELECT * FROM reminder WHERE id=?`, id)
  return row === undefined ? null : toReminder(row)
}

export interface UpsertReminderInput {
  ruleKind: ReminderRuleKind; subjectId: string; duePeriod: string; clientId: string
  docId?: string | null; policyApplied?: 'auto' | 'manual'; now?: string
}

/** Create the reminder for a (rule, subject, period) exactly once. Returns the
 *  existing row's id with created:false when the key is already present. */
export async function upsertReminder(db: DB, input: UpsertReminderInput): Promise<{ id: string; created: boolean }> {
  const id = uuidv7()
  const now = input.now ?? new Date().toISOString()
  const res = await db.run(
    // Portability quirk: ON CONFLICT DO NOTHING is SQLite/Postgres dialect (standard SQL has MERGE).
    `INSERT INTO reminder
       (id, rule_kind, subject_id, due_period, client_id, doc_id, status, policy_applied, error, created_at, sent_at)
     VALUES (?, ?, ?, ?, ?, ?, 'queued', ?, NULL, ?, NULL)
     ON CONFLICT (rule_kind, subject_id, due_period) DO NOTHING`,
    id, input.ruleKind, input.subjectId, input.duePeriod, input.clientId,
    input.docId ?? null, input.policyApplied ?? 'manual', now,
  )
  if (res.changes === 1) {
    await writeAudit(db, 'system', 'create', 'reminder', id, undefined, {
      ruleKind: input.ruleKind, subjectId: input.subjectId, duePeriod: input.duePeriod,
    })
    return { id, created: true }
  }
  const existing = (await db.get<{ id: string }>(
    `SELECT id FROM reminder WHERE rule_kind=? AND subject_id=? AND due_period=?`,
    input.ruleKind, input.subjectId, input.duePeriod,
  ))!
  return { id: existing.id, created: false }
}

export interface ReminderFilter { status?: ReminderStatus; ruleKind?: ReminderRuleKind; clientId?: string }

export async function listReminders(db: DB, filter: ReminderFilter = {}): Promise<Reminder[]> {
  let sql = `SELECT * FROM reminder WHERE 1=1`
  const args: unknown[] = []
  if (filter.status !== undefined) { sql += ` AND status=?`; args.push(filter.status) }
  if (filter.ruleKind !== undefined) { sql += ` AND rule_kind=?`; args.push(filter.ruleKind) }
  if (filter.clientId !== undefined) { sql += ` AND client_id=?`; args.push(filter.clientId) }
  sql += ` ORDER BY id DESC`
  return (await db.all<ReminderRow>(sql, ...args)).map(toReminder)
}

/** Human labels for queue rows — exhaustive so a new rule kind cannot ship unlabelled. */
export const RULE_LABELS: Record<ReminderRuleKind, string> = {
  invoice_overdue: 'Invoice overdue', renewal_due: 'Renewal due', amc_expiring: 'AMC expiring',
  follow_up: 'Follow-up', recurring_generated: 'Recurring invoice', email_bounced: 'Email bounced',
  quote_followup: 'Quote follow-up',
}

export interface QueueItem extends Reminder {
  clientName: string
  docNo: string | null
  /** Derived owner (spec A3): doc_id → document.created_by; null when the reminder has no document. */
  ownerId: string | null
  /** Queue row label, e.g. 'Quote follow-up (d7)'. */
  label: string
}

export interface QueueOpts {
  /** From res.locals.staff — never the request body. Staff are forced to their own rows. */
  viewerRole?: string; viewerId?: string
  /** Narrow to one owner — managerial viewers only (ignored for staff via ownerScope). */
  ownerId?: string
  /** Narrow to one status; default is the working set queued|failed. */
  status?: ReminderStatus
  page?: number; pageSize?: number
}

export interface QueuePage { rows: QueueItem[]; total: number; page: number; pageSize: number }

const QUEUE_PAGE_SIZE = 50
const QUEUE_MAX_PAGE_SIZE = 200

interface QueueRow extends ReminderRow { client_name: string | null; doc_no: string | null; owner_id: string | null }

/** The manual queue: everything awaiting a human — queued items and failed sends.
 *  Paginated with an honest total (rule 8); owner scope derives via
 *  doc_id → document.created_by (spec A3 — no owner column on reminder). */
export async function listQueue(db: DB, opts: QueueOpts = {}): Promise<QueuePage> {
  const page = Math.max(opts.page ?? 1, 1)
  const pageSize = Math.min(Math.max(opts.pageSize ?? QUEUE_PAGE_SIZE, 1), QUEUE_MAX_PAGE_SIZE)
  const scoped = opts.viewerRole !== undefined && opts.viewerId !== undefined
    ? ownerScope({ id: opts.viewerId, role: opts.viewerRole }, opts.ownerId)
    : opts.ownerId
  let where = `r.status IN ('queued','failed')`
  const args: unknown[] = []
  if (opts.status !== undefined) { where = `r.status = ?`; args.push(opts.status) }
  // Owner scope derives via doc_id → document.created_by. Rows with NO document
  // (renewal_due, amc_expiring, follow_up, email_bounced) have no derived owner —
  // they are shared work and stay visible to every viewer, staff included.
  if (scoped !== undefined) { where += ` AND (d.created_by = ? OR r.doc_id IS NULL)`; args.push(scoped) }
  const total = (await db.get<{ n: number }>(
    `SELECT COUNT(*) AS n FROM reminder r LEFT JOIN document d ON d.id = r.doc_id WHERE ${where}`,
    ...args,
  ))!.n
  const rows = await db.all<QueueRow>(
    `SELECT r.*, c.name AS client_name, d.doc_no, d.created_by AS owner_id
     FROM reminder r
     LEFT JOIN client c ON c.id = r.client_id
     LEFT JOIN document d ON d.id = r.doc_id
     WHERE ${where}
     ORDER BY r.id DESC
     LIMIT ? OFFSET ?`,
    ...args, pageSize, (page - 1) * pageSize,
  )
  return {
    rows: rows.map((r) => ({
      ...toReminder(r),
      clientName: r.client_name ?? '',
      docNo: r.doc_no,
      ownerId: r.owner_id,
      label: r.rule_kind === 'quote_followup'
        ? `${RULE_LABELS.quote_followup} (${r.due_period})`
        : RULE_LABELS[r.rule_kind as ReminderRuleKind] ?? r.rule_kind,
    })),
    total, page, pageSize,
  }
}

/** Queue totals (queued/failed) under the same owner scope listQueue applies. */
export async function queueCounts(db: DB, ownerId?: string): Promise<{ queued: number; failed: number }> {
  const rows = await db.all<{ status: string; n: number }>(
    `SELECT r.status, COUNT(*) AS n FROM reminder r LEFT JOIN document d ON d.id = r.doc_id
     WHERE r.status IN ('queued','failed')${ownerId !== undefined ? ` AND (d.created_by = ? OR r.doc_id IS NULL)` : ''}
     GROUP BY r.status`,
    ...(ownerId !== undefined ? [ownerId] : []),
  )
  const by = new Map(rows.map((r) => [r.status, r.n]))
  return { queued: by.get('queued') ?? 0, failed: by.get('failed') ?? 0 }
}

export async function setReminderStatus(
  db: DB, userId: string, id: string, status: ReminderStatus,
  opts: { error?: string | null; sentAt?: string | null } = {},
): Promise<Reminder> {
  const before = await getReminder(db, id)
  if (before === null) throw new Error('Reminder not found')
  await db.run(
    `UPDATE reminder SET status=?, error=?, sent_at=? WHERE id=?`,
    status,
    opts.error !== undefined ? opts.error : before.error,
    opts.sentAt !== undefined ? opts.sentAt : before.sentAt,
    id,
  )
  const after = (await getReminder(db, id))!
  await writeAudit(db, userId, 'update', 'reminder', id, { status: before.status }, { status: after.status, error: after.error })
  return after
}

export async function dismissReminder(db: DB, userId: string, id: string): Promise<Reminder> {
  const before = await getReminder(db, id)
  if (before === null) throw new Error('Reminder not found')
  if (before.status === 'sent') throw new Error('Cannot dismiss a reminder that was already sent')
  return setReminderStatus(db, userId, id, 'dismissed')
}

/**
 * STOP cleanup (spec §7): a quote that is accepted/lost/converted stops chasing.
 * Dismisses every still-open (queued|failed) quote_followup for the quote — one
 * setReminderStatus per row so each dismissal is audited (F14), never a bulk UPDATE.
 * Callers (markStatus / convertDocument) run this inside their own transaction.
 */
export async function dismissQuoteFollowups(db: DB, userId: string, quoteId: string): Promise<number> {
  const rows = await db.all<{ id: string }>(
    `SELECT id FROM reminder
     WHERE rule_kind='quote_followup' AND subject_id=? AND status IN ('queued','failed')`,
    quoteId,
  )
  for (const r of rows) await setReminderStatus(db, userId, r.id, 'dismissed')
  return rows.length
}

// ---------- dated reminder schedule (rule 3 / D-REMIND — spec §4, §7) ----------

/** Rule kinds whose cadence lives in reminder_schedule (dated config rows). */
export type ScheduleRuleKind = 'quote_followup' | 'invoice_overdue'

export interface ResolvedSchedule {
  ruleKind: ScheduleRuleKind
  dayOffsets: number[] // ascending, deduped day milestones since the anchor event
  subject: string | null // message text; null only where the code template owns it
  body: string | null
  source: 'db' | 'default' // whether a dated row resolved or the code constant applied
}

/** Code-constant fallbacks — the feature works before any row is seeded, and a
 *  wiped/missing row can never silence the reminder engine. Cadence *changes*
 *  are new dated rows, never edits here (rule 3). */
export const SCHEDULE_DEFAULTS: Record<
  ScheduleRuleKind, { dayOffsets: number[]; subject: string | null; body: string | null }
> = {
  quote_followup: {
    dayOffsets: [3, 7, 14],
    subject: QUOTE_FOLLOWUP_DEFAULT_SUBJECT,
    body: QUOTE_FOLLOWUP_DEFAULT_BODY,
  },
  // invoice_overdue mail text stays in reminder-templates.ts — only the cadence is dated here.
  invoice_overdue: { dayOffsets: [7, 15, 30], subject: null, body: null },
}

/** Parse a day_offsets CSV ('3,7,14') → ascending unique positive integers.
 *  Lenient — invalid tokens are dropped. Only for READING stored rows, where a
 *  bad token must not silence the whole cadence (resolveSchedule falls back). */
export function parseDayOffsets(csv: string): number[] {
  const days = csv.split(',')
    .map((s) => Number(s.trim()))
    .filter((n) => Number.isInteger(n) && n > 0)
  return [...new Set(days)].sort((a, b) => a - b)
}

/** Strict variant for NEW input (insertSchedule): any token that is not a positive
 *  integer rejects the whole CSV — '3,7,I4' must error, never silently save as
 *  '3,7' and drop a follow-up from the cadence. Spaces and dupes still normalize. */
export function parseDayOffsetsStrict(csv: string): number[] {
  if (csv.trim() === '') throw new Error('dayOffsets must contain at least one positive integer')
  const days = csv.split(',').map((s) => {
    const n = Number(s.trim())
    if (!Number.isInteger(n) || n <= 0) throw new Error(`Invalid day offset '${s.trim()}' — use positive integers like 3,7,14`)
    return n
  })
  return [...new Set(days)].sort((a, b) => a - b)
}

/** Resolve the schedule active on `today` (YYYY-MM-DD): the reminder_schedule row
 *  where effective_from <= today AND (effective_to IS NULL OR effective_to > today),
 *  latest effective_from winning. No usable row → the code-constant default. A row
 *  that sets cadence but leaves subject/body NULL inherits the default message text. */
export async function resolveSchedule(db: DB, ruleKind: ScheduleRuleKind, today: string): Promise<ResolvedSchedule> {
  const fallback = SCHEDULE_DEFAULTS[ruleKind]
  const row = await db.get<{ day_offsets: string; subject: string | null; body: string | null }>(
    `SELECT day_offsets, subject, body FROM reminder_schedule
     WHERE rule_kind=? AND effective_from <= ? AND (effective_to IS NULL OR effective_to > ?)
     ORDER BY effective_from DESC, id DESC LIMIT 1`, // id DESC breaks effective_from ties deterministically (UUIDv7 is time-ordered → latest insert wins on any engine)
    ruleKind, today, today,
  )
  if (row !== undefined) {
    const dayOffsets = parseDayOffsets(row.day_offsets)
    if (dayOffsets.length > 0) {
      return {
        ruleKind, dayOffsets,
        subject: row.subject ?? fallback.subject, body: row.body ?? fallback.body,
        source: 'db',
      }
    }
    // Row present but no usable offsets — never let bad config silence the engine.
  }
  return { ruleKind, dayOffsets: [...fallback.dayOffsets], subject: fallback.subject, body: fallback.body, source: 'default' }
}

export interface ScheduleRow {
  id: string; ruleKind: string; effectiveFrom: string; effectiveTo: string | null
  dayOffsets: string; subject: string | null; body: string | null
}

const SCHEDULE_KINDS = Object.keys(SCHEDULE_DEFAULTS)

/** All dated schedule rows, newest first within each rule kind (bounded set). */
export async function listSchedules(db: DB): Promise<ScheduleRow[]> {
  const rows = await db.all<{ id: string; rule_kind: string; effective_from: string; effective_to: string | null; day_offsets: string; subject: string | null; body: string | null }>(
    `SELECT id, rule_kind, effective_from, effective_to, day_offsets, subject, body
     FROM reminder_schedule ORDER BY rule_kind, effective_from DESC`,
  )
  return rows.map((r) => ({
    id: r.id, ruleKind: r.rule_kind, effectiveFrom: r.effective_from, effectiveTo: r.effective_to,
    dayOffsets: r.day_offsets, subject: r.subject, body: r.body,
  }))
}

/** Append a NEW dated cadence row (rule 3: config change = new row, never an edit). */
export async function insertSchedule(db: DB, userId: string, input: {
  ruleKind: string; effectiveFrom: string; dayOffsets: string; subject?: string; body?: string
}): Promise<ScheduleRow> {
  if (!SCHEDULE_KINDS.includes(input.ruleKind)) throw new Error(`Unknown rule kind: ${input.ruleKind}`)
  if (!/^\d{4}-\d{2}-\d{2}$/.test(input.effectiveFrom)) throw new Error('effectiveFrom must be YYYY-MM-DD')
  const offsets = parseDayOffsetsStrict(input.dayOffsets)
  const id = uuidv7()
  const csv = offsets.join(',')
  await db.transaction(async () => {
    await db.run(
      `INSERT INTO reminder_schedule (id, rule_kind, effective_from, effective_to, day_offsets, subject, body)
       VALUES (?, ?, ?, NULL, ?, ?, ?)`,
      id, input.ruleKind, input.effectiveFrom, csv, input.subject ?? null, input.body ?? null,
    )
    await writeAudit(db, userId, 'create', 'reminder_schedule', id, undefined, {
      ruleKind: input.ruleKind, effectiveFrom: input.effectiveFrom, dayOffsets: csv,
    })
  })
  return (await listSchedules(db)).find((r) => r.id === id)!
}

// ---------- settings helpers (shared by scheduler + bounce poller) ----------

export async function getSetting(db: DB, key: string): Promise<string | null> {
  const row = await db.get<{ value: string }>(`SELECT value FROM setting WHERE key=?`, key)
  return row === undefined ? null : row.value
}

export async function setSetting(db: DB, userId: string, key: string, value: string): Promise<void> {
  const before = await getSetting(db, key)
  await db.run(
    // Portability quirk: ON CONFLICT upsert is SQLite/Postgres dialect (standard SQL has MERGE).
    `INSERT INTO setting (key, value) VALUES (?, ?) ON CONFLICT (key) DO UPDATE SET value = excluded.value`,
    key, value,
  )
  await writeAudit(db, userId, before === null ? 'create' : 'update', 'setting', key, before === null ? undefined : { value: before }, { value })
}

export async function getNumberSetting(db: DB, key: string, fallback: number): Promise<number> {
  const raw = await getSetting(db, key)
  if (raw === null) return fallback
  const n = Number(raw)
  return Number.isFinite(n) ? n : fallback
}