// balance.service.ts — domain service for the Bilan (balance sheet) feature.
//
// Scope at Issue #138 (Bilan #1a): CRUD for `balance_categories` and
// `balance_accounts` only. Snapshots, snapshot lines, transfers and price
// fetching ship in subsequent issues (#1b / #2 / #4 / #5).
//
// CRUD goes through `getDb()` + tauri-plugin-sql directly — the project
// convention for database operations. Tauri commands are reserved for
// filesystem / OAuth / license / profile work and the future Modified Dietz
// + price-fetch work in Issue #142.

import { getDb } from "./db";
import type {
  BalanceAccount,
  BalanceAccountWithCategory,
  BalanceCategory,
  BalanceCategoryKind,
} from "../shared/types";
import { BALANCE_CURRENCY_CAD } from "../shared/types";

// -----------------------------------------------------------------------------
// Errors — typed so the UI can show distinct i18n messages.
// -----------------------------------------------------------------------------

export type BalanceErrorCode =
  | "currency_unsupported"
  | "category_seed_protected"
  | "category_has_accounts"
  | "category_not_found"
  | "account_not_found"
  | "name_required"
  | "kind_invalid";

export class BalanceServiceError extends Error {
  readonly code: BalanceErrorCode;
  constructor(code: BalanceErrorCode, message: string) {
    super(message);
    this.name = "BalanceServiceError";
    this.code = code;
  }
}

// -----------------------------------------------------------------------------
// Categories
// -----------------------------------------------------------------------------

export async function listBalanceCategories(): Promise<BalanceCategory[]> {
  const db = await getDb();
  return db.select<BalanceCategory[]>(
    `SELECT id, key, i18n_key, kind, sort_order, is_active, is_seed
     FROM balance_categories
     ORDER BY sort_order, key`
  );
}

export async function getBalanceCategory(
  id: number
): Promise<BalanceCategory | null> {
  const db = await getDb();
  const rows = await db.select<BalanceCategory[]>(
    `SELECT id, key, i18n_key, kind, sort_order, is_active, is_seed
     FROM balance_categories
     WHERE id = $1`,
    [id]
  );
  return rows[0] ?? null;
}

export interface CreateBalanceCategoryInput {
  key: string;
  i18n_key: string;
  kind: BalanceCategoryKind;
  sort_order?: number;
}

/**
 * Create a user-defined balance category. The seed categories are created by
 * Migration v9 — never call this for seeded keys (UNIQUE will reject the
 * insert anyway).
 *
 * Note (Issue #138): the AccountsPage UI restricts user-created categories to
 * `kind = 'simple'`. The service still accepts both because the priced UI
 * lands in Issue #140.
 */
export async function createBalanceCategory(
  input: CreateBalanceCategoryInput
): Promise<number> {
  if (!input.key || input.key.trim().length === 0) {
    throw new BalanceServiceError("name_required", "Category key is required");
  }
  if (input.kind !== "simple" && input.kind !== "priced") {
    throw new BalanceServiceError("kind_invalid", "Invalid category kind");
  }
  const db = await getDb();
  const result = await db.execute(
    `INSERT INTO balance_categories (key, i18n_key, kind, sort_order, is_active, is_seed)
     VALUES ($1, $2, $3, $4, 1, 0)`,
    [
      input.key.trim(),
      input.i18n_key.trim(),
      input.kind,
      input.sort_order ?? 0,
    ]
  );
  return result.lastInsertId as number;
}

export interface UpdateBalanceCategoryInput {
  i18n_key?: string;
  sort_order?: number;
  is_active?: boolean;
}

/**
 * Rename / re-order / toggle active state of a category. Seeded categories
 * are renamable. Changing `kind` is intentionally not supported (would
 * invalidate existing snapshot lines).
 */
export async function updateBalanceCategory(
  id: number,
  input: UpdateBalanceCategoryInput
): Promise<void> {
  const existing = await getBalanceCategory(id);
  if (!existing) {
    throw new BalanceServiceError(
      "category_not_found",
      `Category ${id} not found`
    );
  }
  const db = await getDb();
  const i18n = input.i18n_key !== undefined ? input.i18n_key : existing.i18n_key;
  const sortOrder =
    input.sort_order !== undefined ? input.sort_order : existing.sort_order;
  const isActive =
    input.is_active !== undefined ? (input.is_active ? 1 : 0) : existing.is_active ? 1 : 0;
  await db.execute(
    `UPDATE balance_categories
       SET i18n_key = $1, sort_order = $2, is_active = $3
     WHERE id = $4`,
    [i18n, sortOrder, isActive, id]
  );
}

/**
 * Delete a user-created category. Refuses to delete:
 *   - seeded categories (`is_seed = 1`) — UI must disable the button;
 *   - categories with linked accounts — FK RESTRICT would also reject, but
 *     we pre-check to surface a clean i18n message.
 */
export async function deleteBalanceCategory(id: number): Promise<void> {
  const existing = await getBalanceCategory(id);
  if (!existing) {
    throw new BalanceServiceError(
      "category_not_found",
      `Category ${id} not found`
    );
  }
  if (existing.is_seed) {
    throw new BalanceServiceError(
      "category_seed_protected",
      "Seeded categories cannot be deleted"
    );
  }
  const db = await getDb();
  const linked = await db.select<Array<{ count: number }>>(
    `SELECT COUNT(*) AS count FROM balance_accounts WHERE balance_category_id = $1`,
    [id]
  );
  if ((linked[0]?.count ?? 0) > 0) {
    throw new BalanceServiceError(
      "category_has_accounts",
      "Cannot delete a category with linked accounts"
    );
  }
  await db.execute("DELETE FROM balance_categories WHERE id = $1", [id]);
}

// -----------------------------------------------------------------------------
// Accounts
// -----------------------------------------------------------------------------

export async function listBalanceAccounts(options?: {
  includeArchived?: boolean;
}): Promise<BalanceAccountWithCategory[]> {
  const includeArchived = options?.includeArchived ?? false;
  const db = await getDb();
  const where = includeArchived
    ? ""
    : "WHERE a.is_active = 1 AND a.archived_at IS NULL";
  return db.select<BalanceAccountWithCategory[]>(
    `SELECT a.id, a.balance_category_id, a.name, a.symbol, a.currency,
            a.notes, a.is_active, a.archived_at, a.created_at, a.updated_at,
            c.key AS category_key, c.i18n_key AS category_i18n_key, c.kind AS category_kind
     FROM balance_accounts a
     INNER JOIN balance_categories c ON c.id = a.balance_category_id
     ${where}
     ORDER BY c.sort_order, a.name`
  );
}

export async function getBalanceAccount(
  id: number
): Promise<BalanceAccount | null> {
  const db = await getDb();
  const rows = await db.select<BalanceAccount[]>(
    `SELECT id, balance_category_id, name, symbol, currency, notes,
            is_active, archived_at, created_at, updated_at
     FROM balance_accounts
     WHERE id = $1`,
    [id]
  );
  return rows[0] ?? null;
}

export interface CreateBalanceAccountInput {
  balance_category_id: number;
  name: string;
  symbol?: string | null;
  /** Defaults to 'CAD'. MVP rejects any other value. */
  currency?: string;
  notes?: string | null;
}

/**
 * Create an account. Currency must be 'CAD' at the MVP — the SQL CHECK
 * would reject anything else, but we pre-check to surface a clean i18n
 * message instead of a raw SQL error.
 */
export async function createBalanceAccount(
  input: CreateBalanceAccountInput
): Promise<number> {
  if (!input.name || input.name.trim().length === 0) {
    throw new BalanceServiceError("name_required", "Account name is required");
  }
  const currency = input.currency ?? BALANCE_CURRENCY_CAD;
  if (currency !== BALANCE_CURRENCY_CAD) {
    throw new BalanceServiceError(
      "currency_unsupported",
      "Only CAD is supported at the MVP"
    );
  }
  const cat = await getBalanceCategory(input.balance_category_id);
  if (!cat) {
    throw new BalanceServiceError(
      "category_not_found",
      "Linked balance category not found"
    );
  }
  const db = await getDb();
  const result = await db.execute(
    `INSERT INTO balance_accounts (balance_category_id, name, symbol, currency, notes, is_active)
     VALUES ($1, $2, $3, $4, $5, 1)`,
    [
      input.balance_category_id,
      input.name.trim(),
      input.symbol ? input.symbol.trim() : null,
      currency,
      input.notes ? input.notes.trim() : null,
    ]
  );
  return result.lastInsertId as number;
}

export interface UpdateBalanceAccountInput {
  balance_category_id?: number;
  name?: string;
  symbol?: string | null;
  notes?: string | null;
  is_active?: boolean;
}

export async function updateBalanceAccount(
  id: number,
  input: UpdateBalanceAccountInput
): Promise<void> {
  const existing = await getBalanceAccount(id);
  if (!existing) {
    throw new BalanceServiceError(
      "account_not_found",
      `Account ${id} not found`
    );
  }
  const name = input.name !== undefined ? input.name.trim() : existing.name;
  if (!name) {
    throw new BalanceServiceError("name_required", "Account name is required");
  }
  const categoryId =
    input.balance_category_id !== undefined
      ? input.balance_category_id
      : existing.balance_category_id;
  const symbol =
    input.symbol !== undefined
      ? input.symbol === null
        ? null
        : input.symbol.trim() || null
      : existing.symbol;
  const notes =
    input.notes !== undefined
      ? input.notes === null
        ? null
        : input.notes.trim() || null
      : existing.notes;
  const isActive =
    input.is_active !== undefined
      ? input.is_active
        ? 1
        : 0
      : existing.is_active
        ? 1
        : 0;
  const db = await getDb();
  await db.execute(
    `UPDATE balance_accounts
       SET balance_category_id = $1, name = $2, symbol = $3, notes = $4,
           is_active = $5, updated_at = CURRENT_TIMESTAMP
     WHERE id = $6`,
    [categoryId, name, symbol, notes, isActive, id]
  );
}

/**
 * Soft-delete an account: stamp `archived_at` and set `is_active = 0`.
 * Archived accounts are hidden from new snapshots but kept in the historic
 * snapshot lines (which is why we never hard-delete here).
 */
export async function archiveBalanceAccount(id: number): Promise<void> {
  const existing = await getBalanceAccount(id);
  if (!existing) {
    throw new BalanceServiceError(
      "account_not_found",
      `Account ${id} not found`
    );
  }
  const db = await getDb();
  await db.execute(
    `UPDATE balance_accounts
       SET archived_at = CURRENT_TIMESTAMP, is_active = 0,
           updated_at = CURRENT_TIMESTAMP
     WHERE id = $1`,
    [id]
  );
}

export async function unarchiveBalanceAccount(id: number): Promise<void> {
  const existing = await getBalanceAccount(id);
  if (!existing) {
    throw new BalanceServiceError(
      "account_not_found",
      `Account ${id} not found`
    );
  }
  const db = await getDb();
  await db.execute(
    `UPDATE balance_accounts
       SET archived_at = NULL, is_active = 1,
           updated_at = CURRENT_TIMESTAMP
     WHERE id = $1`,
    [id]
  );
}