// Package tenant provides middleware for cross-tenant access prevention.
package tenant

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/jfraeys/fetch_ml/internal/logging"
)

// Context key for storing tenant ID
type contextKey string

const (
	// ContextTenantID is the key for tenant ID in context
	ContextTenantID contextKey = "tenant_id"
	// ContextUserID is the key for user ID in context
	ContextUserID contextKey = "user_id"
)

// Middleware provides HTTP middleware for tenant isolation
type Middleware struct {
	tenantManager *Manager
	logger        *logging.Logger
}

// NewMiddleware creates a new tenant middleware
func NewMiddleware(tm *Manager, logger *logging.Logger) *Middleware {
	return &Middleware{
		tenantManager: tm,
		logger:        logger,
	}
}

// ExtractTenantID extracts tenant ID from request headers or context
func ExtractTenantID(r *http.Request) string {
	// Check header first
	tenantID := r.Header.Get("X-Tenant-ID")
	if tenantID != "" {
		return tenantID
	}

	// Check query parameter
	tenantID = r.URL.Query().Get("tenant_id")
	if tenantID != "" {
		return tenantID
	}

	// Check context (set by upstream middleware)
	if ctxTenantID := r.Context().Value(ContextTenantID); ctxTenantID != nil {
		if id, ok := ctxTenantID.(string); ok {
			return id
		}
	}

	return ""
}

// Handler wraps an HTTP handler with tenant validation
func (m *Middleware) Handler(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		tenantID := ExtractTenantID(r)

		if tenantID == "" {
			m.logger.Warn("request without tenant ID",
				"path", r.URL.Path,
				"remote_addr", r.RemoteAddr,
			)
			http.Error(w, "Tenant ID required", http.StatusBadRequest)
			return
		}

		// Validate tenant exists and is active
		tenant, err := m.tenantManager.GetTenant(tenantID)
		if err != nil {
			m.logger.Warn("invalid tenant ID",
				"tenant_id", tenantID,
				"path", r.URL.Path,
				"error", err,
			)
			http.Error(w, "Invalid tenant", http.StatusForbidden)
			return
		}

		// Add tenant to context
		ctx := context.WithValue(r.Context(), ContextTenantID, tenantID)
		ctx = context.WithValue(ctx, ContextUserID, r.Header.Get("X-User-ID"))

		// Log access
		m.logger.Debug("tenant request",
			"tenant_id", tenantID,
			"tenant_name", tenant.Name,
			"path", r.URL.Path,
			"method", r.Method,
		)

		// Audit log
		if err := m.tenantManager.auditLog.LogEvent(ctx, AuditEvent{
			Type:      AuditResourceAccess,
			TenantID:  tenantID,
			Timestamp: time.Now().UTC(),
			Success:   true,
			Details: map[string]any{
				"path":   r.URL.Path,
				"method": r.Method,
			},
			IPAddress: extractIP(r.RemoteAddr),
		}); err != nil {
			m.logger.Warn("failed to log audit event", "error", err)
		}

		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

// ResourceAccessChecker validates access to resources across tenants
type ResourceAccessChecker struct {
	tenantManager *Manager
	logger        *logging.Logger
}

// NewResourceAccessChecker creates a new resource access checker
func NewResourceAccessChecker(tm *Manager, logger *logging.Logger) *ResourceAccessChecker {
	return &ResourceAccessChecker{
		tenantManager: tm,
		logger:        logger,
	}
}

// CheckAccess validates if a tenant can access a specific resource
func (rac *ResourceAccessChecker) CheckAccess(ctx context.Context, resourceTenantID string) error {
	requestingTenantID := GetTenantIDFromContext(ctx)
	if requestingTenantID == "" {
		return fmt.Errorf("no tenant ID in context")
	}

	// Same tenant - always allowed
	if requestingTenantID == resourceTenantID {
		return nil
	}

	// Cross-tenant access - deny by default
	rac.logger.Warn("cross-tenant access denied",
		"requesting_tenant", requestingTenantID,
		"resource_tenant", resourceTenantID,
	)

	// Audit the denial
	userID := GetUserIDFromContext(ctx)
	if err := rac.tenantManager.auditLog.LogEvent(ctx, AuditEvent{
		Type:      AuditCrossTenantDeny,
		TenantID:  requestingTenantID,
		UserID:    userID,
		Timestamp: time.Now().UTC(),
		Success:   false,
		Details: map[string]any{
			"target_tenant": resourceTenantID,
			"reason":        "cross-tenant access not permitted",
		},
	}); err != nil {
		rac.logger.Warn("failed to log audit event", "error", err)
	}

	return fmt.Errorf("cross-tenant access denied: cannot access resources belonging to tenant %s", resourceTenantID)
}

// CheckResourceOwnership validates that a resource belongs to the requesting tenant
func (rac *ResourceAccessChecker) CheckResourceOwnership(ctx context.Context, resourceID, resourceTenantID string) error {
	return rac.CheckAccess(ctx, resourceTenantID)
}

// GetTenantIDFromContext extracts tenant ID from context
func GetTenantIDFromContext(ctx context.Context) string {
	if tenantID := ctx.Value(ContextTenantID); tenantID != nil {
		if id, ok := tenantID.(string); ok {
			return id
		}
	}
	return ""
}

// GetUserIDFromContext extracts user ID from context
func GetUserIDFromContext(ctx context.Context) string {
	if userID := ctx.Value(ContextUserID); userID != nil {
		if id, ok := userID.(string); ok {
			return id
		}
	}
	return ""
}

// WithTenantContext creates a context with tenant ID for background operations
func WithTenantContext(parent context.Context, tenantID, userID string) context.Context {
	ctx := context.WithValue(parent, ContextTenantID, tenantID)
	if userID != "" {
		ctx = context.WithValue(ctx, ContextUserID, userID)
	}
	return ctx
}

// IsolatedPath returns a tenant-isolated path for storing resources
func IsolatedPath(basePath, tenantID, resourceType, resourceID string) string {
	return fmt.Sprintf("%s/%s/%s/%s", basePath, tenantID, resourceType, resourceID)
}

// ValidateResourcePath ensures a path is within the tenant's isolated workspace
func ValidateResourcePath(basePath, tenantID, requestedPath string) error {
	expectedPrefix := fmt.Sprintf("%s/%s/", basePath, tenantID)
	if !strings.HasPrefix(requestedPath, expectedPrefix) {
		return fmt.Errorf("path %s is outside tenant %s workspace", requestedPath, tenantID)
	}
	return nil
}

// extractIP extracts the IP address from RemoteAddr
func extractIP(remoteAddr string) string {
	// Handle "IP:port" format
	if idx := strings.LastIndex(remoteAddr, ":"); idx != -1 {
		return remoteAddr[:idx]
	}
	return remoteAddr
}