package controlplane

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/base64"
	"errors"
	"fmt"
	"image/png"
	"strings"
	"time"

	"aigw/internal/security"

	"github.com/jackc/pgx/v5"
	"github.com/pquerna/otp"
	"github.com/pquerna/otp/totp"
)

func (s *Store) MFAMethods(ctx context.Context, userID string) ([]string, error) {
	var totpEnabled, passkeyEnabled, recoveryEnabled bool
	if err := s.db.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM console_totp_credentials WHERE user_id=$1 AND confirmed_at IS NOT NULL),
		EXISTS(SELECT 1 FROM console_passkeys WHERE user_id=$1),
		EXISTS(SELECT 1 FROM console_recovery_codes WHERE user_id=$1 AND used_at IS NULL)`, userID).
		Scan(&totpEnabled, &passkeyEnabled, &recoveryEnabled); err != nil {
		return nil, err
	}
	methods := make([]string, 0, 3)
	if totpEnabled {
		methods = append(methods, "totp")
	}
	if passkeyEnabled {
		methods = append(methods, "passkey")
	}
	if recoveryEnabled {
		methods = append(methods, "recovery")
	}
	return methods, nil
}

func (s *Store) MFAStatus(ctx context.Context, userID string) (MFAStatus, error) {
	var result MFAStatus
	if err := s.db.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM console_totp_credentials
		WHERE user_id=$1 AND confirmed_at IS NOT NULL)`, userID).Scan(&result.TOTPEnabled); err != nil {
		return MFAStatus{}, err
	}
	passkeys, err := s.ListPasskeys(ctx, userID)
	if err != nil {
		return MFAStatus{}, err
	}
	result.Passkeys = passkeys
	return result, nil
}

func (s *Store) FindActiveConsoleUser(ctx context.Context, email string) (ConsoleActor, error) {
	var actor ConsoleActor
	err := s.db.QueryRow(ctx, `SELECT id::text,COALESCE(tenant_id::text,''),email,display_name,role
		FROM console_users WHERE lower(email)=$1 AND status='active' AND email_verified_at IS NOT NULL`,
		strings.ToLower(strings.TrimSpace(email))).Scan(&actor.ID, &actor.TenantID, &actor.Email, &actor.DisplayName, &actor.Role)
	if errors.Is(err, pgx.ErrNoRows) {
		return ConsoleActor{}, ErrConsoleUnauthorized
	}
	return actor, err
}

func (s *Store) VerifyConsolePassword(ctx context.Context, userID, password string) error {
	var expectedHash, salt []byte
	var iterations int
	if err := s.db.QueryRow(ctx, `SELECT password_hash,password_salt,password_iterations FROM console_users
		WHERE id=$1 AND status='active'`, userID).Scan(&expectedHash, &salt, &iterations); err != nil {
		return ErrConsoleUnauthorized
	}
	if !security.VerifyPassword(password, expectedHash, salt, iterations) {
		return ErrConsoleUnauthorized
	}
	return nil
}

func (s *Store) ResolveMFAChallenge(ctx context.Context, rawToken, remoteIP string) (string, string, error) {
	hash := sha256.Sum256([]byte(strings.TrimSpace(rawToken)))
	var id, userID, expectedIP string
	err := s.db.QueryRow(ctx, `SELECT id::text,user_id::text,COALESCE(host(remote_ip),'')
		FROM console_auth_challenges WHERE token_hash=$1 AND purpose='mfa_login'
		AND consumed_at IS NULL AND expires_at>now()`, hash[:]).Scan(&id, &userID, &expectedIP)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", "", ErrActionTokenInvalid
	}
	if err != nil {
		return "", "", err
	}
	if expectedIP != "" && remoteIP != "" && expectedIP != remoteIP {
		return "", "", ErrActionTokenInvalid
	}
	return id, userID, nil
}

func (s *Store) VerifyTOTPForUser(ctx context.Context, userID, code string) error {
	tx, err := s.db.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)
	var ciphertext []byte
	var lastStep int64
	if err := tx.QueryRow(ctx, `SELECT secret_ciphertext,last_used_step FROM console_totp_credentials
		WHERE user_id=$1 AND confirmed_at IS NOT NULL FOR UPDATE`, userID).Scan(&ciphertext, &lastStep); err != nil {
		return ErrConsoleUnauthorized
	}
	secret, err := s.cipher.Decrypt(ciphertext)
	if err != nil {
		return err
	}
	step, ok := matchingTOTPStep(secret, strings.TrimSpace(code), time.Now().UTC())
	if !ok || step <= lastStep {
		return ErrConsoleUnauthorized
	}
	if _, err := tx.Exec(ctx, `UPDATE console_totp_credentials SET last_used_step=$2 WHERE user_id=$1`, userID, step); err != nil {
		return err
	}
	return tx.Commit(ctx)
}

func (s *Store) BeginMFAChallenge(ctx context.Context, actor ConsoleActor, remoteIP, userAgent string) (AuthChallenge, error) {
	methods, err := s.MFAMethods(ctx, actor.ID)
	if err != nil {
		return AuthChallenge{}, err
	}
	if len(methods) == 0 {
		return AuthChallenge{}, ErrActionTokenInvalid
	}
	raw, hash, err := randomCredential("mfa-aigw-")
	if err != nil {
		return AuthChallenge{}, err
	}
	expires := time.Now().UTC().Add(10 * time.Minute)
	_, err = s.db.Exec(ctx, `INSERT INTO console_auth_challenges
		(user_id,token_hash,purpose,allowed_methods,expires_at,remote_ip,user_agent)
		VALUES ($1,$2,'mfa_login',$3,$4,NULLIF($5,'')::inet,$6)`, actor.ID, hash, methods, expires, remoteIP, userAgent)
	if err != nil {
		return AuthChallenge{}, fmt.Errorf("create MFA challenge: %w", err)
	}
	return AuthChallenge{Token: raw, Methods: methods, ExpiresAt: expires}, nil
}

func (s *Store) BeginTOTP(ctx context.Context, actor ConsoleActor) (TOTPEnrollment, error) {
	key, err := totp.Generate(totp.GenerateOpts{Issuer: "AIGW", AccountName: actor.Email, Period: 30, SecretSize: 20, Digits: otp.DigitsSix, Algorithm: otp.AlgorithmSHA1})
	if err != nil {
		return TOTPEnrollment{}, fmt.Errorf("generate TOTP secret: %w", err)
	}
	ciphertext, err := s.cipher.Encrypt(key.Secret())
	if err != nil {
		return TOTPEnrollment{}, err
	}
	result, err := s.db.Exec(ctx, `INSERT INTO console_totp_credentials (user_id,secret_ciphertext,confirmed_at,last_used_step)
		VALUES ($1,$2,NULL,-1) ON CONFLICT (user_id) DO UPDATE SET secret_ciphertext=EXCLUDED.secret_ciphertext,
		confirmed_at=NULL,last_used_step=-1,created_at=now()
		WHERE console_totp_credentials.confirmed_at IS NULL`, actor.ID, ciphertext)
	if err != nil {
		return TOTPEnrollment{}, fmt.Errorf("store TOTP enrollment: %w", err)
	}
	if result.RowsAffected() == 0 {
		return TOTPEnrollment{}, errors.New("TOTP is already enabled")
	}
	var image bytes.Buffer
	qr, err := key.Image(256, 256)
	if err == nil {
		err = png.Encode(&image, qr)
	}
	if err != nil {
		return TOTPEnrollment{}, fmt.Errorf("render TOTP QR: %w", err)
	}
	return TOTPEnrollment{Secret: key.Secret(), URI: key.URL(), QRCode: "data:image/png;base64," + base64.StdEncoding.EncodeToString(image.Bytes())}, nil
}

func (s *Store) ConfirmTOTP(ctx context.Context, actorID, code string) ([]string, error) {
	code = strings.TrimSpace(code)
	tx, err := s.db.Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer tx.Rollback(ctx)
	var ciphertext []byte
	var confirmed *time.Time
	if err := tx.QueryRow(ctx, `SELECT secret_ciphertext,confirmed_at FROM console_totp_credentials WHERE user_id=$1 FOR UPDATE`, actorID).Scan(&ciphertext, &confirmed); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, errors.New("TOTP enrollment has not started")
		}
		return nil, err
	}
	secret, err := s.cipher.Decrypt(ciphertext)
	if err != nil {
		return nil, err
	}
	step, ok := matchingTOTPStep(secret, code, time.Now().UTC())
	if !ok {
		return nil, errors.New("invalid TOTP code")
	}
	if confirmed != nil {
		return nil, errors.New("TOTP is already enabled")
	}
	if _, err := tx.Exec(ctx, `UPDATE console_totp_credentials SET confirmed_at=now(),last_used_step=$2 WHERE user_id=$1`, actorID, step); err != nil {
		return nil, err
	}
	if _, err := tx.Exec(ctx, `DELETE FROM console_recovery_codes WHERE user_id=$1`, actorID); err != nil {
		return nil, err
	}
	codes := make([]string, 0, 10)
	for i := 0; i < 10; i++ {
		code, hash, err := newRecoveryCode()
		if err != nil {
			return nil, err
		}
		if _, err := tx.Exec(ctx, `INSERT INTO console_recovery_codes (user_id,code_hash) VALUES ($1,$2)`, actorID, hash); err != nil {
			return nil, err
		}
		codes = append(codes, code)
	}
	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}
	return codes, nil
}

func (s *Store) DisableTOTP(ctx context.Context, actorID string) error {
	tx, err := s.db.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)
	if _, err := tx.Exec(ctx, `DELETE FROM console_totp_credentials WHERE user_id=$1`, actorID); err != nil {
		return err
	}
	if _, err := tx.Exec(ctx, `DELETE FROM console_recovery_codes WHERE user_id=$1`, actorID); err != nil {
		return err
	}
	return tx.Commit(ctx)
}

func (s *Store) CompleteMFAChallenge(ctx context.Context, input MFACodeInput, remoteIP string) (ConsoleActor, string, error) {
	code := strings.TrimSpace(input.Code)
	tokenHash := sha256.Sum256([]byte(strings.TrimSpace(input.ChallengeToken)))
	tx, err := s.db.Begin(ctx)
	if err != nil {
		return ConsoleActor{}, "", err
	}
	defer tx.Rollback(ctx)
	var challengeID, userID, expectedIP string
	var allowed []string
	err = tx.QueryRow(ctx, `SELECT c.id::text,c.user_id::text,COALESCE(host(c.remote_ip),''),c.allowed_methods
		FROM console_auth_challenges c WHERE c.token_hash=$1 AND c.purpose='mfa_login'
		AND c.consumed_at IS NULL AND c.expires_at>now() FOR UPDATE`, tokenHash[:]).Scan(&challengeID, &userID, &expectedIP, &allowed)
	if errors.Is(err, pgx.ErrNoRows) {
		return ConsoleActor{}, "", ErrActionTokenInvalid
	}
	if err != nil {
		return ConsoleActor{}, "", err
	}
	if expectedIP != "" && remoteIP != "" && expectedIP != remoteIP {
		return ConsoleActor{}, "", ErrActionTokenInvalid
	}
	var method string
	if method = "totp"; len(code) != 6 {
		method = "recovery"
	}
	valid := false
	if method == "totp" {
		var ciphertext []byte
		var lastStep int64
		if err := tx.QueryRow(ctx, `SELECT secret_ciphertext,last_used_step FROM console_totp_credentials WHERE user_id=$1 AND confirmed_at IS NOT NULL FOR UPDATE`, userID).Scan(&ciphertext, &lastStep); err == nil {
			secret, decryptErr := s.cipher.Decrypt(ciphertext)
			if decryptErr == nil {
				if step, ok := matchingTOTPStep(secret, code, time.Now().UTC()); ok && step > lastStep {
					valid = true
					if _, err := tx.Exec(ctx, `UPDATE console_totp_credentials SET last_used_step=$2 WHERE user_id=$1`, userID, step); err != nil {
						return ConsoleActor{}, "", err
					}
				}
			}
		}
	}
	if !valid && method == "recovery" {
		hash := sha256.Sum256([]byte(normalizeRecoveryCode(code)))
		result, updateErr := tx.Exec(ctx, `UPDATE console_recovery_codes SET used_at=now()
			WHERE user_id=$1 AND code_hash=$2 AND used_at IS NULL`, userID, hash[:])
		valid = updateErr == nil && result.RowsAffected() == 1
	}
	if !valid {
		_, _ = tx.Exec(ctx, `UPDATE console_auth_challenges SET attempts=attempts+1,
			consumed_at=CASE WHEN attempts+1 >= 5 THEN now() ELSE consumed_at END WHERE id=$1`, challengeID)
		if err := tx.Commit(ctx); err != nil {
			return ConsoleActor{}, "", err
		}
		return ConsoleActor{}, "", ErrConsoleUnauthorized
	}
	if _, err := tx.Exec(ctx, `UPDATE console_auth_challenges SET consumed_at=now() WHERE id=$1`, challengeID); err != nil {
		return ConsoleActor{}, "", err
	}
	var actor ConsoleActor
	if err := tx.QueryRow(ctx, `SELECT id::text,COALESCE(tenant_id::text,''),email,display_name,role FROM console_users WHERE id=$1 AND status='active'`, userID).
		Scan(&actor.ID, &actor.TenantID, &actor.Email, &actor.DisplayName, &actor.Role); err != nil {
		return ConsoleActor{}, "", err
	}
	if err := tx.Commit(ctx); err != nil {
		return ConsoleActor{}, "", err
	}
	return actor, method, nil
}

func matchingTOTPStep(secret, code string, now time.Time) (int64, bool) {
	if len(strings.TrimSpace(code)) != 6 {
		return 0, false
	}
	current := now.Unix() / 30
	opts := totp.ValidateOpts{Period: 30, Skew: 0, Digits: otp.DigitsSix, Algorithm: otp.AlgorithmSHA1}
	for _, step := range []int64{current - 1, current, current + 1} {
		generated, err := totp.GenerateCodeCustom(secret, time.Unix(step*30, 0), opts)
		if err == nil && generated == code {
			return step, true
		}
	}
	return 0, false
}

func newRecoveryCode() (string, []byte, error) {
	raw, _, err := randomCredential("")
	if err != nil {
		return "", nil, err
	}
	value := strings.ToUpper(strings.TrimRight(raw, "="))
	if len(value) > 10 {
		value = value[:10]
	}
	if len(value) < 10 {
		return newRecoveryCode()
	}
	code := value[:5] + "-" + value[5:]
	hash := sha256.Sum256([]byte(normalizeRecoveryCode(code)))
	return code, hash[:], nil
}

func normalizeRecoveryCode(value string) string {
	return strings.ToUpper(strings.ReplaceAll(strings.TrimSpace(value), "-", ""))
}