package auth

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

	"github.com/lib/pq"
)

// Common errors.
var (
	ErrKeyNotFound = errors.New("api key not found")
	ErrKeyRevoked  = errors.New("api key has been revoked")
	ErrKeyExpired  = errors.New("api key has expired")
)

// APIKey represents a stored API key.
type APIKey struct {
	ID          string
	Name        string
	KeyPrefix   string
	Scopes      []Scope
	ProjectIDs  []string // nil = all projects
	CreatedAt   time.Time
	ExpiresAt   *time.Time
	LastUsedAt  *time.Time
	RevokedAt   *time.Time
	CreatedBy   string
}

// IsExpired checks if the key has expired.
func (k *APIKey) IsExpired() bool {
	if k.ExpiresAt == nil {
		return false
	}
	return time.Now().After(*k.ExpiresAt)
}

// IsRevoked checks if the key has been revoked.
func (k *APIKey) IsRevoked() bool {
	return k.RevokedAt != nil
}

// IsActive checks if the key is valid for use.
func (k *APIKey) IsActive() bool {
	return !k.IsRevoked() && !k.IsExpired()
}

// CreateKeyRequest is the input for creating a new key.
type CreateKeyRequest struct {
	Name       string
	Scopes     []Scope
	ProjectIDs []string      // nil = all projects
	ExpiresIn  time.Duration // 0 = never
	CreatedBy  string
}

// CreateKeyResponse is the output of creating a new key.
type CreateKeyResponse struct {
	Key    *APIKey
	Secret string // Full key, shown only once
}

// Service handles API key operations.
type Service struct {
	db       *sql.DB
	adminKey string // Super admin key from environment
}

// NewService creates a new auth service.
func NewService(db *sql.DB, adminKey string) *Service {
	return &Service{
		db:       db,
		adminKey: adminKey,
	}
}

// IsAdminKey checks if the provided key is the super admin key.
func (s *Service) IsAdminKey(key string) bool {
	return s.adminKey != "" && key == s.adminKey
}

// Create generates a new API key.
func (s *Service) Create(ctx context.Context, req CreateKeyRequest) (*CreateKeyResponse, error) {
	// Validate scopes
	if !ValidateScopes(req.Scopes) {
		return nil, fmt.Errorf("invalid scopes")
	}

	// Generate key
	fullKey, prefix, err := GenerateKey()
	if err != nil {
		return nil, fmt.Errorf("generate key: %w", err)
	}

	keyHash := HashKey(fullKey)
	expiresAt := ExpiresAt(req.ExpiresIn)

	// Convert scopes to strings for postgres
	scopeStrings := ScopesToStrings(req.Scopes)

	var id string
	err = s.db.QueryRowContext(ctx, `
		INSERT INTO api_keys (name, key_hash, key_prefix, scopes, project_ids, expires_at, created_by)
		VALUES ($1, $2, $3, $4, $5, $6, $7)
		RETURNING id
	`, req.Name, keyHash, prefix, pq.Array(scopeStrings), pq.Array(req.ProjectIDs), expiresAt, req.CreatedBy).Scan(&id)

	if err != nil {
		return nil, fmt.Errorf("insert key: %w", err)
	}

	key := &APIKey{
		ID:         id,
		Name:       req.Name,
		KeyPrefix:  prefix,
		Scopes:     req.Scopes,
		ProjectIDs: req.ProjectIDs,
		CreatedAt:  time.Now(),
		ExpiresAt:  expiresAt,
		CreatedBy:  req.CreatedBy,
	}

	return &CreateKeyResponse{
		Key:    key,
		Secret: fullKey,
	}, nil
}

// Validate checks if a key is valid and returns the key details.
func (s *Service) Validate(ctx context.Context, key string) (*APIKey, error) {
	// Check admin key first
	if s.IsAdminKey(key) {
		return &APIKey{
			ID:        "admin",
			Name:      "Super Admin",
			KeyPrefix: "admin",
			Scopes:    []Scope{ScopeAdmin},
			CreatedAt: time.Time{},
		}, nil
	}

	// Validate format
	if !ValidateKeyFormat(key) {
		return nil, ErrKeyNotFound
	}

	keyHash := HashKey(key)

	var (
		apiKey       APIKey
		scopeStrings []string
	)

	err := s.db.QueryRowContext(ctx, `
		SELECT id, name, key_prefix, scopes, project_ids, created_at, expires_at, last_used_at, revoked_at, created_by
		FROM api_keys
		WHERE key_hash = $1
	`, keyHash).Scan(
		&apiKey.ID,
		&apiKey.Name,
		&apiKey.KeyPrefix,
		pq.Array(&scopeStrings),
		pq.Array(&apiKey.ProjectIDs),
		&apiKey.CreatedAt,
		&apiKey.ExpiresAt,
		&apiKey.LastUsedAt,
		&apiKey.RevokedAt,
		&apiKey.CreatedBy,
	)

	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrKeyNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("query key: %w", err)
	}

	apiKey.Scopes = ScopesFromStrings(scopeStrings)

	if apiKey.IsRevoked() {
		return nil, ErrKeyRevoked
	}

	if apiKey.IsExpired() {
		return nil, ErrKeyExpired
	}

	// Update last_used_at asynchronously
	go func() {
		s.db.ExecContext(context.Background(), `
			UPDATE api_keys SET last_used_at = NOW() WHERE id = $1
		`, apiKey.ID)
	}()

	return &apiKey, nil
}

// List returns all API keys (without secrets).
func (s *Service) List(ctx context.Context) ([]*APIKey, error) {
	rows, err := s.db.QueryContext(ctx, `
		SELECT id, name, key_prefix, scopes, project_ids, created_at, expires_at, last_used_at, revoked_at, created_by
		FROM api_keys
		ORDER BY created_at DESC
	`)
	if err != nil {
		return nil, fmt.Errorf("query keys: %w", err)
	}
	defer rows.Close()

	var keys []*APIKey
	for rows.Next() {
		var (
			key          APIKey
			scopeStrings []string
		)
		if err := rows.Scan(
			&key.ID,
			&key.Name,
			&key.KeyPrefix,
			pq.Array(&scopeStrings),
			pq.Array(&key.ProjectIDs),
			&key.CreatedAt,
			&key.ExpiresAt,
			&key.LastUsedAt,
			&key.RevokedAt,
			&key.CreatedBy,
		); err != nil {
			return nil, fmt.Errorf("scan key: %w", err)
		}
		key.Scopes = ScopesFromStrings(scopeStrings)
		keys = append(keys, &key)
	}

	return keys, nil
}

// Get returns a single API key by ID.
func (s *Service) Get(ctx context.Context, id string) (*APIKey, error) {
	var (
		key          APIKey
		scopeStrings []string
	)

	err := s.db.QueryRowContext(ctx, `
		SELECT id, name, key_prefix, scopes, project_ids, created_at, expires_at, last_used_at, revoked_at, created_by
		FROM api_keys
		WHERE id = $1
	`, id).Scan(
		&key.ID,
		&key.Name,
		&key.KeyPrefix,
		pq.Array(&scopeStrings),
		pq.Array(&key.ProjectIDs),
		&key.CreatedAt,
		&key.ExpiresAt,
		&key.LastUsedAt,
		&key.RevokedAt,
		&key.CreatedBy,
	)

	if errors.Is(err, sql.ErrNoRows) {
		return nil, ErrKeyNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("query key: %w", err)
	}

	key.Scopes = ScopesFromStrings(scopeStrings)
	return &key, nil
}

// Revoke marks an API key as revoked.
func (s *Service) Revoke(ctx context.Context, id string) error {
	result, err := s.db.ExecContext(ctx, `
		UPDATE api_keys SET revoked_at = NOW()
		WHERE id = $1 AND revoked_at IS NULL
	`, id)
	if err != nil {
		return fmt.Errorf("revoke key: %w", err)
	}

	rows, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("rows affected: %w", err)
	}

	if rows == 0 {
		return ErrKeyNotFound
	}

	return nil
}