package auth

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/go-webauthn/webauthn/webauthn"
)

type Repository struct {
	db *sql.DB
}

func NewRepository(db *sql.DB) *Repository {
	return &Repository{db: db}
}

func (r *Repository) UpsertUser(ctx context.Context, user User) (User, error) {
	now := time.Now().UTC()
	if user.ID == "" {
		user.ID = "user:" + user.Email
	}
	if user.Role == "" {
		user.Role = RoleViewer
	}
	if user.DisplayName == "" {
		user.DisplayName = user.Email
	}

	if _, err := r.db.ExecContext(ctx, `
		INSERT INTO users (id, email, display_name, password_hash, role, created_at, last_seen_at)
		VALUES (?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT(email) DO UPDATE SET
			display_name = excluded.display_name,
			password_hash = COALESCE(excluded.password_hash, users.password_hash),
			role = excluded.role,
			last_seen_at = excluded.last_seen_at
	`, user.ID, user.Email, user.DisplayName, nullString(user.PasswordHash), string(user.Role), now.Format(time.RFC3339), now.Format(time.RFC3339)); err != nil {
		return User{}, fmt.Errorf("upsert user: %w", err)
	}

	return r.GetUserByEmail(ctx, user.Email)
}

func (r *Repository) GetUserByEmail(ctx context.Context, email string) (User, error) {
	var user User
	var created, lastSeen, passwordHash, role string
	err := r.db.QueryRowContext(ctx, `
		SELECT id, email, COALESCE(display_name, ''), COALESCE(password_hash, ''), COALESCE(role, 'viewer'), created_at, COALESCE(last_seen_at, '')
		FROM users
		WHERE email = ?
	`, email).Scan(&user.ID, &user.Email, &user.DisplayName, &passwordHash, &role, &created, &lastSeen)
	if err != nil {
		return User{}, err
	}
	user.PasswordHash = passwordHash
	user.Role = Role(role)
	user.CreatedAt, err = time.Parse(time.RFC3339, created)
	if err != nil {
		return User{}, fmt.Errorf("parse user created_at: %w", err)
	}
	if lastSeen != "" {
		user.LastSeenAt, err = time.Parse(time.RFC3339, lastSeen)
		if err != nil {
			return User{}, fmt.Errorf("parse user last_seen_at: %w", err)
		}
	}
	user.Credentials, err = r.ListCredentials(ctx, user.ID)
	if err != nil {
		return User{}, err
	}
	return user, nil
}

func (r *Repository) GetUserByID(ctx context.Context, userID string) (User, error) {
	var email string
	if err := r.db.QueryRowContext(ctx, `SELECT email FROM users WHERE id = ?`, userID).Scan(&email); err != nil {
		return User{}, err
	}
	return r.GetUserByEmail(ctx, email)
}

func (r *Repository) CountUsers(ctx context.Context) (int, error) {
	var count int
	if err := r.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM users`).Scan(&count); err != nil {
		return 0, err
	}
	return count, nil
}

func (r *Repository) CountAdmins(ctx context.Context) (int, error) {
	var count int
	if err := r.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM users WHERE role = 'admin'`).Scan(&count); err != nil {
		return 0, err
	}
	return count, nil
}

func (r *Repository) ListUsers(ctx context.Context) ([]User, error) {
	rows, err := r.db.QueryContext(ctx, `
		SELECT id, email, COALESCE(display_name, ''), COALESCE(password_hash, ''), COALESCE(role, 'viewer'), created_at, COALESCE(last_seen_at, '')
		FROM users
		ORDER BY created_at DESC
	`)
	if err != nil {
		return nil, fmt.Errorf("list users: %w", err)
	}
	defer rows.Close()

	var users []User
	for rows.Next() {
		var user User
		var created, lastSeen, role string
		if err := rows.Scan(&user.ID, &user.Email, &user.DisplayName, &user.PasswordHash, &role, &created, &lastSeen); err != nil {
			return nil, fmt.Errorf("scan user: %w", err)
		}
		user.Role = Role(role)
		user.CreatedAt, _ = time.Parse(time.RFC3339, created)
		if lastSeen != "" {
			user.LastSeenAt, _ = time.Parse(time.RFC3339, lastSeen)
		}
		users = append(users, user)
	}
	return users, rows.Err()
}

func (r *Repository) UpdatePasswordHash(ctx context.Context, userID, passwordHash string) error {
	result, err := r.db.ExecContext(ctx, `
		UPDATE users
		SET password_hash = ?, last_seen_at = ?
		WHERE id = ?
	`, passwordHash, time.Now().UTC().Format(time.RFC3339), userID)
	if err != nil {
		return err
	}
	if rows, _ := result.RowsAffected(); rows == 0 {
		return sql.ErrNoRows
	}
	return nil
}

func (r *Repository) UpdateUserRole(ctx context.Context, userID string, role Role) error {
	result, err := r.db.ExecContext(ctx, `
		UPDATE users
		SET role = ?, last_seen_at = ?
		WHERE id = ?
	`, string(role), time.Now().UTC().Format(time.RFC3339), userID)
	if err != nil {
		return err
	}
	if rows, _ := result.RowsAffected(); rows == 0 {
		return sql.ErrNoRows
	}
	return nil
}

func (r *Repository) DeleteUser(ctx context.Context, userID string) error {
	result, err := r.db.ExecContext(ctx, `DELETE FROM users WHERE id = ?`, userID)
	if err != nil {
		return err
	}
	if rows, _ := result.RowsAffected(); rows == 0 {
		return sql.ErrNoRows
	}
	return nil
}

func (r *Repository) SaveCredential(ctx context.Context, userID string, credential webauthn.Credential) error {
	now := time.Now().UTC().Format(time.RFC3339)
	payload, err := json.Marshal(credential)
	if err != nil {
		return fmt.Errorf("marshal credential: %w", err)
	}
	if _, err := r.db.ExecContext(ctx, `
		INSERT INTO webauthn_credentials (id, user_id, credential_id, credential_json, created_at, last_used_at)
		VALUES (?, ?, ?, ?, ?, ?)
		ON CONFLICT(credential_id) DO UPDATE SET
			credential_json = excluded.credential_json,
			last_used_at = excluded.last_used_at
	`, "cred:"+hashSecret(string(credential.ID))[:24], userID, credential.ID, string(payload), now, now); err != nil {
		return fmt.Errorf("save credential: %w", err)
	}
	return nil
}

func (r *Repository) ListCredentials(ctx context.Context, userID string) ([]webauthn.Credential, error) {
	rows, err := r.db.QueryContext(ctx, `
		SELECT credential_json
		FROM webauthn_credentials
		WHERE user_id = ?
		ORDER BY created_at ASC
	`, userID)
	if err != nil {
		return nil, fmt.Errorf("list credentials: %w", err)
	}
	defer rows.Close()

	var credentials []webauthn.Credential
	for rows.Next() {
		var raw string
		if err := rows.Scan(&raw); err != nil {
			return nil, fmt.Errorf("scan credential: %w", err)
		}
		var credential webauthn.Credential
		if err := json.Unmarshal([]byte(raw), &credential); err != nil {
			return nil, fmt.Errorf("unmarshal credential: %w", err)
		}
		credentials = append(credentials, credential)
	}
	return credentials, rows.Err()
}

func (r *Repository) SaveChallenge(ctx context.Context, userID, challengeType string, session webauthn.SessionData, ttl time.Duration) (string, error) {
	idPart, err := randomToken(18)
	if err != nil {
		return "", err
	}
	payload, err := json.Marshal(session)
	if err != nil {
		return "", fmt.Errorf("marshal challenge: %w", err)
	}
	now := time.Now().UTC()
	id := "chal:" + idPart
	if _, err := r.db.ExecContext(ctx, `
		INSERT INTO auth_challenges (id, user_id, type, session_json, created_at, expires_at)
		VALUES (?, ?, ?, ?, ?, ?)
	`, id, userID, challengeType, string(payload), now.Format(time.RFC3339), now.Add(ttl).Format(time.RFC3339)); err != nil {
		return "", fmt.Errorf("save challenge: %w", err)
	}
	return id, nil
}

func (r *Repository) ConsumeChallenge(ctx context.Context, id, challengeType string) (webauthn.SessionData, string, error) {
	var raw, userID, expires, used string
	err := r.db.QueryRowContext(ctx, `
		SELECT session_json, user_id, expires_at, COALESCE(used_at, '')
		FROM auth_challenges
		WHERE id = ? AND type = ?
	`, id, challengeType).Scan(&raw, &userID, &expires, &used)
	if err != nil {
		return webauthn.SessionData{}, "", err
	}
	if used != "" {
		return webauthn.SessionData{}, "", fmt.Errorf("challenge already used")
	}
	expiresAt, err := time.Parse(time.RFC3339, expires)
	if err != nil {
		return webauthn.SessionData{}, "", fmt.Errorf("parse challenge expiry: %w", err)
	}
	if time.Now().UTC().After(expiresAt) {
		return webauthn.SessionData{}, "", fmt.Errorf("challenge expired")
	}
	var session webauthn.SessionData
	if err := json.Unmarshal([]byte(raw), &session); err != nil {
		return webauthn.SessionData{}, "", fmt.Errorf("unmarshal challenge: %w", err)
	}
	if _, err := r.db.ExecContext(ctx, `UPDATE auth_challenges SET used_at = ? WHERE id = ?`, time.Now().UTC().Format(time.RFC3339), id); err != nil {
		return webauthn.SessionData{}, "", fmt.Errorf("consume challenge: %w", err)
	}
	return session, userID, nil
}

func (r *Repository) CreateSession(ctx context.Context, userID, tokenHash, ip, userAgent string, ttl time.Duration) (Session, error) {
	idPart, err := randomToken(18)
	if err != nil {
		return Session{}, err
	}
	now := time.Now().UTC()
	session := Session{
		ID:        "sess:" + idPart,
		UserID:    userID,
		TokenHash: tokenHash,
		CreatedAt: now,
		ExpiresAt: now.Add(ttl),
	}
	if _, err := r.db.ExecContext(ctx, `
		INSERT INTO sessions (id, user_id, token_hash, created_at, expires_at, last_seen_at, ip_address, user_agent)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?)
	`, session.ID, session.UserID, session.TokenHash, session.CreatedAt.Format(time.RFC3339), session.ExpiresAt.Format(time.RFC3339), now.Format(time.RFC3339), ip, userAgent); err != nil {
		return Session{}, fmt.Errorf("create session: %w", err)
	}
	return session, nil
}

func (r *Repository) ValidateSession(ctx context.Context, tokenHash string) (Session, User, error) {
	var session Session
	var created, expires, revoked string
	err := r.db.QueryRowContext(ctx, `
		SELECT id, user_id, token_hash, created_at, expires_at, COALESCE(revoked_at, '')
		FROM sessions
		WHERE token_hash = ?
	`, tokenHash).Scan(&session.ID, &session.UserID, &session.TokenHash, &created, &expires, &revoked)
	if err != nil {
		return Session{}, User{}, err
	}
	session.CreatedAt, err = time.Parse(time.RFC3339, created)
	if err != nil {
		return Session{}, User{}, err
	}
	session.ExpiresAt, err = time.Parse(time.RFC3339, expires)
	if err != nil {
		return Session{}, User{}, err
	}
	if revoked != "" {
		return Session{}, User{}, fmt.Errorf("session revoked")
	}
	if time.Now().UTC().After(session.ExpiresAt) {
		return Session{}, User{}, fmt.Errorf("session expired")
	}
	user, err := r.GetUserByID(ctx, session.UserID)
	if err != nil {
		return Session{}, User{}, err
	}
	_, _ = r.db.ExecContext(ctx, `UPDATE sessions SET last_seen_at = ? WHERE id = ?`, time.Now().UTC().Format(time.RFC3339), session.ID)
	return session, user, nil
}

func (r *Repository) RevokeSession(ctx context.Context, sessionID string) error {
	_, err := r.db.ExecContext(ctx, `UPDATE sessions SET revoked_at = ? WHERE id = ?`, time.Now().UTC().Format(time.RFC3339), sessionID)
	return err
}

func (r *Repository) CreateAPIKey(ctx context.Context, key APIKey) error {
	if _, err := r.db.ExecContext(ctx, `
		INSERT INTO api_keys (id, user_id, name, key_hash, scopes, created_at, expires_at, last_used_at, revoked_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
	`, key.ID, key.UserID, key.Name, key.KeyHash, scopesToString(key.Scopes), key.CreatedAt.Format(time.RFC3339), timePtrString(key.ExpiresAt), timePtrString(key.LastUsedAt), timePtrString(key.RevokedAt)); err != nil {
		return fmt.Errorf("create api key: %w", err)
	}
	return nil
}

func (r *Repository) ValidateAPIKey(ctx context.Context, keyID, keyHash string) (APIKey, User, error) {
	var key APIKey
	var scopesRaw, created, expires, lastUsed, revoked string
	err := r.db.QueryRowContext(ctx, `
		SELECT id, user_id, name, key_hash, scopes, created_at, COALESCE(expires_at, ''), COALESCE(last_used_at, ''), COALESCE(revoked_at, '')
		FROM api_keys
		WHERE id = ?
	`, keyID).Scan(&key.ID, &key.UserID, &key.Name, &key.KeyHash, &scopesRaw, &created, &expires, &lastUsed, &revoked)
	if err != nil {
		return APIKey{}, User{}, err
	}
	if !constantTimeEqualHex(key.KeyHash, keyHash) {
		return APIKey{}, User{}, sql.ErrNoRows
	}
	key.Scopes = scopesFromString(scopesRaw)
	key.CreatedAt, err = time.Parse(time.RFC3339, created)
	if err != nil {
		return APIKey{}, User{}, err
	}
	if expires != "" {
		parsed, err := time.Parse(time.RFC3339, expires)
		if err != nil {
			return APIKey{}, User{}, err
		}
		if time.Now().UTC().After(parsed) {
			return APIKey{}, User{}, fmt.Errorf("api key expired")
		}
		key.ExpiresAt = &parsed
	}
	if revoked != "" {
		return APIKey{}, User{}, fmt.Errorf("api key revoked")
	}
	if lastUsed != "" {
		parsed, err := time.Parse(time.RFC3339, lastUsed)
		if err == nil {
			key.LastUsedAt = &parsed
		}
	}
	user, err := r.GetUserByID(ctx, key.UserID)
	if err != nil {
		return APIKey{}, User{}, err
	}
	_, _ = r.db.ExecContext(ctx, `UPDATE api_keys SET last_used_at = ? WHERE id = ?`, time.Now().UTC().Format(time.RFC3339), key.ID)
	return key, user, nil
}

func (r *Repository) ListAPIKeys(ctx context.Context, userID string) ([]APIKey, error) {
	rows, err := r.db.QueryContext(ctx, `
		SELECT id, user_id, name, scopes, created_at, COALESCE(expires_at, ''), COALESCE(last_used_at, ''), COALESCE(revoked_at, '')
		FROM api_keys
		WHERE user_id = ?
		ORDER BY created_at DESC
	`, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var keys []APIKey
	for rows.Next() {
		var key APIKey
		var scopesRaw, created, expires, lastUsed, revoked string
		if err := rows.Scan(&key.ID, &key.UserID, &key.Name, &scopesRaw, &created, &expires, &lastUsed, &revoked); err != nil {
			return nil, err
		}
		key.Scopes = scopesFromString(scopesRaw)
		key.CreatedAt, _ = time.Parse(time.RFC3339, created)
		if expires != "" {
			parsed, _ := time.Parse(time.RFC3339, expires)
			key.ExpiresAt = &parsed
		}
		if lastUsed != "" {
			parsed, _ := time.Parse(time.RFC3339, lastUsed)
			key.LastUsedAt = &parsed
		}
		if revoked != "" {
			parsed, _ := time.Parse(time.RFC3339, revoked)
			key.RevokedAt = &parsed
		}
		keys = append(keys, key)
	}
	return keys, rows.Err()
}

func (r *Repository) RevokeAPIKey(ctx context.Context, userID, keyID string) error {
	result, err := r.db.ExecContext(ctx, `UPDATE api_keys SET revoked_at = ? WHERE id = ? AND user_id = ?`, time.Now().UTC().Format(time.RFC3339), keyID, userID)
	if err != nil {
		return err
	}
	if rows, _ := result.RowsAffected(); rows == 0 {
		return sql.ErrNoRows
	}
	return nil
}

func (r *Repository) CreateDeviceCode(ctx context.Context, device DeviceCode) error {
	_, err := r.db.ExecContext(ctx, `
		INSERT INTO device_codes (id, device_code_hash, user_code_hash, user_code_display, name, scopes, status, created_at, expires_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
	`, device.ID, device.DeviceCodeHash, device.UserCodeHash, device.UserCodeDisplay, device.Name, scopesToString(device.Scopes), device.Status, device.CreatedAt.Format(time.RFC3339), device.ExpiresAt.Format(time.RFC3339))
	return err
}

func (r *Repository) GetDeviceCodeByUserCode(ctx context.Context, userCodeHash string) (DeviceCode, error) {
	return r.getDeviceCode(ctx, `user_code_hash = ?`, userCodeHash)
}

func (r *Repository) GetDeviceCodeByDeviceCode(ctx context.Context, deviceCodeHash string) (DeviceCode, error) {
	return r.getDeviceCode(ctx, `device_code_hash = ?`, deviceCodeHash)
}

func (r *Repository) getDeviceCode(ctx context.Context, predicate string, value string) (DeviceCode, error) {
	var device DeviceCode
	var scopesRaw, created, expires, approved, lastPolled, userID string
	row := r.db.QueryRowContext(ctx, `
		SELECT id, COALESCE(user_id, ''), device_code_hash, user_code_hash, user_code_display, name, scopes, status, created_at, expires_at, COALESCE(approved_at, ''), COALESCE(last_polled_at, '')
		FROM device_codes
		WHERE `+predicate, value)
	if err := row.Scan(&device.ID, &userID, &device.DeviceCodeHash, &device.UserCodeHash, &device.UserCodeDisplay, &device.Name, &scopesRaw, &device.Status, &created, &expires, &approved, &lastPolled); err != nil {
		return DeviceCode{}, err
	}
	device.UserID = userID
	device.Scopes = scopesFromString(scopesRaw)
	device.CreatedAt, _ = time.Parse(time.RFC3339, created)
	device.ExpiresAt, _ = time.Parse(time.RFC3339, expires)
	if approved != "" {
		parsed, _ := time.Parse(time.RFC3339, approved)
		device.ApprovedAt = &parsed
	}
	if lastPolled != "" {
		parsed, _ := time.Parse(time.RFC3339, lastPolled)
		device.LastPolledAt = &parsed
	}
	if time.Now().UTC().After(device.ExpiresAt) && device.Status == "pending" {
		device.Status = "expired"
		_, _ = r.db.ExecContext(ctx, `UPDATE device_codes SET status = 'expired' WHERE id = ?`, device.ID)
	}
	return device, nil
}

func (r *Repository) ApproveDeviceCode(ctx context.Context, userCodeHash, userID string) (DeviceCode, error) {
	now := time.Now().UTC().Format(time.RFC3339)
	result, err := r.db.ExecContext(ctx, `
		UPDATE device_codes
		SET status = 'approved', user_id = ?, approved_at = ?
		WHERE user_code_hash = ? AND status = 'pending'
	`, userID, now, userCodeHash)
	if err != nil {
		return DeviceCode{}, err
	}
	if rows, _ := result.RowsAffected(); rows == 0 {
		return DeviceCode{}, sql.ErrNoRows
	}
	return r.GetDeviceCodeByUserCode(ctx, userCodeHash)
}

func (r *Repository) TouchDevicePoll(ctx context.Context, id string) {
	_, _ = r.db.ExecContext(ctx, `UPDATE device_codes SET last_polled_at = ? WHERE id = ?`, time.Now().UTC().Format(time.RFC3339), id)
}

func (r *Repository) FinishDeviceCode(ctx context.Context, id string) {
	_, _ = r.db.ExecContext(ctx, `UPDATE device_codes SET status = 'expired', last_polled_at = ? WHERE id = ?`, time.Now().UTC().Format(time.RFC3339), id)
}

func (r *Repository) Audit(ctx context.Context, actorUserID, eventType, resourceType, resourceID, ip, userAgent string, metadata map[string]any) {
	idPart, err := randomToken(18)
	if err != nil {
		return
	}
	if metadata == nil {
		metadata = map[string]any{}
	}
	payload, err := json.Marshal(metadata)
	if err != nil {
		payload = []byte("{}")
	}
	_, _ = r.db.ExecContext(ctx, `
		INSERT INTO audit_log (id, actor_user_id, event_type, resource_type, resource_id, ip_address, user_agent, created_at, metadata_json)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
	`, "audit:"+idPart, nullString(actorUserID), eventType, nullString(resourceType), nullString(resourceID), ip, userAgent, time.Now().UTC().Format(time.RFC3339), string(payload))
}

func nullString(value string) any {
	if value == "" {
		return nil
	}
	return value
}

func timePtrString(value *time.Time) any {
	if value == nil {
		return nil
	}
	return value.UTC().Format(time.RFC3339)
}

func isNoRows(err error) bool {
	return errors.Is(err, sql.ErrNoRows)
}