import { and, asc, eq, getTableColumns, inArray, like, sql } from "drizzle-orm";
import { pluginSettings, users } from "../db/schema.js";
import type { DatabaseContext } from "./database-context.js";
import {
  countValue,
  rowsAffected,
  supportsReturning,
} from "./mutation-result.js";
import { insertReturning, updateReturning } from "./returning.js";

/** isExternal: the user has at least one external sign-in identity. */
export type UserRecord = typeof users.$inferSelect & { isExternal: boolean };
export type NewUserRecord = typeof users.$inferInsert;
export type UserUpdate = Partial<Omit<NewUserRecord, "id">>;
export type NewFirstLocalUserRecord = Omit<NewUserRecord, "isAdmin">;

// Qualified by hand: drizzle prints a column in a subquery without its table,
// which would bind users.id to the identity row's own id.
const userColumns = {
  ...getTableColumns(users),
  isExternal:
    sql<boolean>`EXISTS (SELECT 1 FROM ${sql.identifier("user_external_identities")} WHERE ${sql.identifier("user_external_identities")}.${sql.identifier("user_id")} = ${sql.identifier("users")}.${sql.identifier("id")})`.mapWith(
      (value: unknown) => value === true || Number(value) === 1,
    ),
};

// The unique-violation codes of better-sqlite3, node-postgres and mysql2.
const UNIQUE_VIOLATION_CODES = new Set([
  "SQLITE_CONSTRAINT_UNIQUE",
  "23505",
  "ER_DUP_ENTRY",
]);

/**
 * Whether creating a user failed because the username is taken. The id is
 * generated, so the username index is the only one a new row can collide on.
 * drizzle wraps driver errors, so the code may sit on a cause.
 */
export function isUsernameTaken(error: unknown): boolean {
  for (let e = error; e instanceof Error; e = e.cause) {
    if (UNIQUE_VIOLATION_CODES.has((e as { code?: string }).code ?? "")) {
      return true;
    }
  }
  return false;
}

export class UserRepository {
  constructor(
    private readonly context: DatabaseContext,
    private readonly onWrite?: () => void | Promise<void>,
  ) {}

  async listAll(): Promise<UserRecord[]> {
    return this.context.drizzle.select(userColumns).from(users);
  }

  /**
   * One page of users, optionally filtered by username.
   *
   * The admin panel used to render every account at once, which is fine at
   * home and not fine on a directory-backed install with thousands of them.
   * Sorted by username so paging is stable between requests.
   */
  async listPage(input: {
    search?: string;
    limit: number;
    offset: number;
  }): Promise<{ users: UserRecord[]; total: number }> {
    const term = input.search?.trim();
    const where = term
      ? like(sql`lower(${users.username})`, `%${term.toLowerCase()}%`)
      : undefined;

    const [rows, totalResult] = await Promise.all([
      this.context.drizzle
        .select(userColumns)
        .from(users)
        .where(where)
        // Case-insensitive: a plain sort puts every capitalised name ahead of
        // every lowercase one, which reads as unordered in the admin list.
        .orderBy(asc(sql`lower(${users.username})`))
        .limit(input.limit)
        .offset(input.offset),
      this.context.drizzle
        .select({ count: sql<number>`COUNT(*)` })
        .from(users)
        .where(where),
    ]);

    return { users: rows, total: countValue(totalResult[0]?.count) };
  }

  async findById(id: string): Promise<UserRecord | null> {
    const rows = await this.context.drizzle
      .select(userColumns)
      .from(users)
      .where(eq(users.id, id))
      .limit(1);

    return rows[0] ?? null;
  }

  async findByUsername(username: string): Promise<UserRecord | null> {
    const rows = await this.context.drizzle
      .select(userColumns)
      .from(users)
      .where(eq(users.username, username))
      .limit(1);

    return rows[0] ?? null;
  }

  async listByIds(ids: string[]): Promise<UserRecord[]> {
    const uniqueIds = Array.from(new Set(ids.filter(Boolean)));
    if (uniqueIds.length === 0) {
      return [];
    }

    return this.context.drizzle
      .select(userColumns)
      .from(users)
      .where(inArray(users.id, uniqueIds));
  }

  async create(user: NewUserRecord): Promise<UserRecord> {
    const rows = await insertReturning(this.context, users, user);
    await this.afterWrite();
    return (
      (await this.findById(rows[0].id)) ?? { ...rows[0], isExternal: false }
    );
  }

  async createFirstLocalUser(
    user: NewFirstLocalUserRecord,
  ): Promise<{ user: UserRecord; isFirstUser: boolean }> {
    const result = await this.createCheckingIfFirst((isFirstUser) => ({
      ...user,
      isAdmin: isFirstUser,
    }));

    await this.afterWrite();
    return { ...result, user: { ...result.user, isExternal: false } };
  }

  async createFirstSsoUser(
    user: NewUserRecord,
  ): Promise<{ user: UserRecord; isFirstUser: boolean }> {
    const result = await this.createCheckingIfFirst((isFirstUser) => ({
      ...user,
      isAdmin: isFirstUser || Boolean(user.isAdmin),
    }));

    await this.afterWrite();
    return { ...result, user: { ...result.user, isExternal: true } };
  }

  /**
   * Creates a user, making them an admin if the table was empty.
   *
   * The check and the insert have to be one transaction: two people signing up
   * at once would otherwise both see an empty table and both become admin.
   *
   * The two branches are not a style choice. better-sqlite3 is synchronous and
   * rejects an async transaction callback outright, "Transaction function
   * cannot return a promise", so a single body cannot serve both. It fails
   * loudly rather than silently skipping the write, which is the one mercy here.
   */
  private async createCheckingIfFirst(
    build: (isFirstUser: boolean) => NewUserRecord,
  ): Promise<{ user: typeof users.$inferSelect; isFirstUser: boolean }> {
    if (this.context.dialect === "sqlite") {
      /* eslint-disable no-restricted-syntax -- sqlite-only branch: the dialect
         is checked directly above, and better-sqlite3 rejects an async
         transaction callback, so this cannot use the shared helpers. */
      return this.context.drizzle.transaction((tx) => {
        const isFirstUser =
          tx.select({ id: users.id }).from(users).all().length === 0;
        const rows = tx
          .insert(users)
          .values(build(isFirstUser))
          .returning()
          .all();
        return { user: rows[0], isFirstUser };
      });
      /* eslint-enable no-restricted-syntax */
    }

    return this.context.drizzle.transaction(async (tx) => {
      const existing = await tx.select({ id: users.id }).from(users);
      const isFirstUser = existing.length === 0;
      const values = build(isFirstUser);

      if (supportsReturning(this.context.dialect)) {
        // eslint-disable-next-line no-restricted-syntax -- guarded by the check on this line
        const rows = await tx.insert(users).values(values).returning();
        return { user: rows[0], isFirstUser };
      }

      // users is keyed by a text id the caller supplies, so there is something
      // to read back by even without RETURNING.
      await tx.insert(users).values(values);
      const [user] = await tx
        .select()
        .from(users)
        .where(eq(users.id, values.id));
      return { user, isFirstUser };
    });
  }

  async update(id: string, update: UserUpdate): Promise<UserRecord | null> {
    const rows = await updateReturning(
      this.context,
      users,
      update,
      eq(users.id, id),
    );

    await this.afterWrite();
    return rows[0] ? this.findById(rows[0].id) : null;
  }

  async delete(id: string): Promise<boolean> {
    // plugin_settings.scope_id is polymorphic, so it carries no foreign key to
    // users and the engine will not cascade it. Removed here rather than in a
    // route so every caller that deletes a user is covered.
    await this.context.drizzle
      .delete(pluginSettings)
      .where(
        and(
          inArray(pluginSettings.scope, ["user", "secret"]),
          eq(pluginSettings.scopeId, id),
        ),
      );

    const result = await this.context.drizzle
      .delete(users)
      .where(eq(users.id, id));

    await this.afterWrite();
    return rowsAffected(result) > 0;
  }

  async countAdmins(): Promise<number> {
    const rows = await this.context.drizzle
      .select({ id: users.id })
      .from(users)
      .where(eq(users.isAdmin, true));

    return rows.length;
  }

  async countAll(): Promise<number> {
    const rows = await this.context.drizzle
      .select({ id: users.id })
      .from(users);

    return rows.length;
  }

  private async afterWrite(): Promise<void> {
    await this.onWrite?.();
  }
}