// service.ts
//
// Core authentication service providing login, logout, registration,
// password reset, and email verification.

import type { Request as ExpressRequest } from "express";
import { AnonymousUser, type User, type UserId } from "../user";
import { hashPassword, verifyPassword } from "./password";
import type { AuthStore } from "./store";
import {
    hashToken,
    parseAuthorizationHeader,
    SESSION_COOKIE_NAME,
} from "./token";
import { type SessionData, type TokenId, tokenLifetimes } from "./types";

type LoginResult =
    | { success: true; token: string; user: User }
    | { success: false; error: string };

type RegisterResult =
    | { success: true; user: User; verificationToken: string }
    | { success: false; error: string };

type SimpleResult = { success: true } | { success: false; error: string };

// Result of validating a request/token - contains both user and session
export type AuthResult =
    | { authenticated: true; user: User; session: SessionData }
    | { authenticated: false; user: typeof AnonymousUser; session: null };

export class AuthService {
    constructor(private store: AuthStore) {}

    // === Login ===

    async login(
        email: string,
        password: string,
        authMethod: "cookie" | "bearer",
        metadata?: { userAgent?: string; ipAddress?: string },
    ): Promise<LoginResult> {
        const user = await this.store.getUserByEmail(email);
        if (!user) {
            return { success: false, error: "Invalid credentials" };
        }

        if (!user.isActive()) {
            return { success: false, error: "Account is not active" };
        }

        const passwordHash = await this.store.getUserPasswordHash(user.id);
        if (!passwordHash) {
            return { success: false, error: "Invalid credentials" };
        }

        const valid = await verifyPassword(password, passwordHash);
        if (!valid) {
            return { success: false, error: "Invalid credentials" };
        }

        const { token } = await this.store.createSession({
            userId: user.id,
            tokenType: "session",
            authMethod,
            expiresAt: new Date(Date.now() + tokenLifetimes.session),
            userAgent: metadata?.userAgent,
            ipAddress: metadata?.ipAddress,
        });

        return { success: true, token, user };
    }

    // === Session Validation ===

    async validateRequest(request: ExpressRequest): Promise<AuthResult> {
        // Try cookie first (for web requests)
        let token = this.extractCookieToken(request);

        // Fall back to Authorization header (for API requests)
        if (!token) {
            token = parseAuthorizationHeader(request.get("Authorization"));
        }

        if (!token) {
            return { authenticated: false, user: AnonymousUser, session: null };
        }

        return this.validateToken(token);
    }

    async validateToken(token: string): Promise<AuthResult> {
        const tokenId = hashToken(token) as TokenId;
        const session = await this.store.getSession(tokenId);

        if (!session) {
            return { authenticated: false, user: AnonymousUser, session: null };
        }

        if (session.tokenType !== "session") {
            return { authenticated: false, user: AnonymousUser, session: null };
        }

        const user = await this.store.getUserById(session.userId as UserId);
        if (!user || !user.isActive()) {
            return { authenticated: false, user: AnonymousUser, session: null };
        }

        // Update last used (fire and forget)
        this.store.updateLastUsed(tokenId).catch(() => {});

        return { authenticated: true, user, session };
    }

    private extractCookieToken(request: ExpressRequest): string | null {
        const cookies = request.get("Cookie");
        if (!cookies) {
            return null;
        }

        for (const cookie of cookies.split(";")) {
            const [name, ...valueParts] = cookie.trim().split("=");
            if (name === SESSION_COOKIE_NAME) {
                return valueParts.join("="); // Handle = in token value
            }
        }
        return null;
    }

    // === Logout ===

    async logout(token: string): Promise<void> {
        const tokenId = hashToken(token) as TokenId;
        await this.store.deleteSession(tokenId);
    }

    async logoutAllSessions(userId: UserId): Promise<number> {
        return this.store.deleteUserSessions(userId);
    }

    // === Registration ===

    async register(
        email: string,
        password: string,
        displayName?: string,
    ): Promise<RegisterResult> {
        const existing = await this.store.getUserByEmail(email);
        if (existing) {
            return { success: false, error: "Email already registered" };
        }

        const passwordHash = await hashPassword(password);
        const user = await this.store.createUser({
            email,
            passwordHash,
            displayName,
        });

        // Create email verification token
        const { token: verificationToken } = await this.store.createSession({
            userId: user.id,
            tokenType: "email_verify",
            authMethod: "bearer",
            expiresAt: new Date(Date.now() + tokenLifetimes.email_verify),
        });

        return { success: true, user, verificationToken };
    }

    // === Email Verification ===

    async verifyEmail(token: string): Promise<SimpleResult> {
        const tokenId = hashToken(token) as TokenId;
        const session = await this.store.getSession(tokenId);

        if (!session || session.tokenType !== "email_verify") {
            return {
                success: false,
                error: "Invalid or expired verification token",
            };
        }

        if (session.isUsed) {
            return { success: false, error: "Token already used" };
        }

        await this.store.updateUserEmailVerified(session.userId as UserId);
        await this.store.deleteSession(tokenId);

        return { success: true };
    }

    // === Password Reset ===

    async createPasswordResetToken(
        email: string,
    ): Promise<{ token: string } | null> {
        const user = await this.store.getUserByEmail(email);
        if (!user) {
            // Don't reveal whether email exists
            return null;
        }

        const { token } = await this.store.createSession({
            userId: user.id,
            tokenType: "password_reset",
            authMethod: "bearer",
            expiresAt: new Date(Date.now() + tokenLifetimes.password_reset),
        });

        return { token };
    }

    async resetPassword(
        token: string,
        newPassword: string,
    ): Promise<SimpleResult> {
        const tokenId = hashToken(token) as TokenId;
        const session = await this.store.getSession(tokenId);

        if (!session || session.tokenType !== "password_reset") {
            return { success: false, error: "Invalid or expired reset token" };
        }

        if (session.isUsed) {
            return { success: false, error: "Token already used" };
        }

        const passwordHash = await hashPassword(newPassword);
        await this.store.setUserPassword(
            session.userId as UserId,
            passwordHash,
        );

        // Invalidate all existing sessions (security: password changed)
        await this.store.deleteUserSessions(session.userId as UserId);

        // Delete the reset token
        await this.store.deleteSession(tokenId);

        return { success: true };
    }

    // === Token Extraction Helper (for routes) ===

    extractToken(request: ExpressRequest): string | null {
        // Try Authorization header first
        const token = parseAuthorizationHeader(request.get("Authorization"));
        if (token) {
            return token;
        }

        // Try cookie
        return this.extractCookieToken(request);
    }
}