package validation

import (
	"context"
	"encoding/json"
	"fmt"
	"meteor-compute-service/internal/models"
	"time"
	
	"github.com/google/uuid"
)

// Validator interface defines the contract for event validation
type Validator interface {
	Validate(ctx context.Context, rawEvent *models.RawEvent) (*models.ValidationResult, error)
}

// MVPValidator implements a basic pass-through validation for MVP
// This will be replaced with more sophisticated algorithms in Epic 3
type MVPValidator struct {
	algorithmName string
	version       string
}

// NewMVPValidator creates a new MVP validator instance
func NewMVPValidator() *MVPValidator {
	return &MVPValidator{
		algorithmName: "mvp_pass_through",
		version:       "1.0.0",
	}
}

// Validate performs basic validation on a raw event
// For MVP, this is a simple pass-through that marks all events as valid
func (v *MVPValidator) Validate(ctx context.Context, rawEvent *models.RawEvent) (*models.ValidationResult, error) {
	// Basic validation details that will be stored
	details := ValidationDetails{
		Algorithm:       v.algorithmName,
		Version:         v.version,
		ValidationSteps: []ValidationStep{},
		Metadata:        make(map[string]interface{}),
	}

	// Step 1: Basic data completeness check
	step1 := v.validateDataCompleteness(rawEvent)
	details.ValidationSteps = append(details.ValidationSteps, step1)

	// Step 2: Event type validation
	step2 := v.validateEventType(rawEvent)
	details.ValidationSteps = append(details.ValidationSteps, step2)

	// Step 3: File validation
	step3 := v.validateFile(rawEvent)
	details.ValidationSteps = append(details.ValidationSteps, step3)

	// Step 4: Metadata validation
	step4 := v.validateMetadata(rawEvent)
	details.ValidationSteps = append(details.ValidationSteps, step4)

	// For MVP, calculate a simple score based on completed validation steps
	totalSteps := len(details.ValidationSteps)
	passedSteps := 0
	for _, step := range details.ValidationSteps {
		if step.Passed {
			passedSteps++
		}
	}

	score := float64(passedSteps) / float64(totalSteps)
	isValid := score >= 0.8 // 80% threshold for MVP

	// Add summary to metadata
	details.Metadata["total_steps"] = totalSteps
	details.Metadata["passed_steps"] = passedSteps
	details.Metadata["score"] = score
	details.Metadata["threshold"] = 0.8

	// Serialize details to JSON
	detailsJSON, err := json.Marshal(details)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal validation details: %w", err)
	}

	return &models.ValidationResult{
		IsValid:     isValid,
		Score:       score,
		Algorithm:   v.algorithmName,
		Details:     detailsJSON,
		ProcessedAt: time.Now().UTC(),
		Reason:      v.generateReason(isValid, passedSteps, totalSteps),
	}, nil
}

// ValidationDetails represents the detailed validation information
type ValidationDetails struct {
	Algorithm       string                 `json:"algorithm"`
	Version         string                 `json:"version"`
	ValidationSteps []ValidationStep       `json:"validation_steps"`
	Metadata        map[string]interface{} `json:"metadata"`
}

// ValidationStep represents a single validation step
type ValidationStep struct {
	Name        string                 `json:"name"`
	Description string                 `json:"description"`
	Passed      bool                   `json:"passed"`
	Details     map[string]interface{} `json:"details,omitempty"`
	Error       string                 `json:"error,omitempty"`
}

// validateDataCompleteness checks if required fields are present
func (v *MVPValidator) validateDataCompleteness(rawEvent *models.RawEvent) ValidationStep {
	step := ValidationStep{
		Name:        "data_completeness",
		Description: "Checks if required fields are present and valid",
		Details:     make(map[string]interface{}),
	}

	issues := []string{}

	// Check required UUID fields
	if rawEvent.ID == (uuid.UUID{}) {
		issues = append(issues, "missing_id")
	}
	if rawEvent.DeviceID == (uuid.UUID{}) {
		issues = append(issues, "missing_device_id")
	}
	if rawEvent.UserProfileID == (uuid.UUID{}) {
		issues = append(issues, "missing_user_profile_id")
	}

	// Check required string fields
	if rawEvent.FilePath == "" {
		issues = append(issues, "missing_file_path")
	}
	if rawEvent.EventType == "" {
		issues = append(issues, "missing_event_type")
	}

	// Check timestamp
	if rawEvent.EventTimestamp.IsZero() {
		issues = append(issues, "missing_event_timestamp")
	}

	step.Details["issues"] = issues
	step.Details["issues_count"] = len(issues)
	step.Passed = len(issues) == 0

	if len(issues) > 0 {
		step.Error = fmt.Sprintf("Found %d data completeness issues", len(issues))
	}

	return step
}

// validateEventType checks if the event type is supported
func (v *MVPValidator) validateEventType(rawEvent *models.RawEvent) ValidationStep {
	step := ValidationStep{
		Name:        "event_type_validation",
		Description: "Validates that the event type is supported",
		Details:     make(map[string]interface{}),
	}

	supportedTypes := []string{
		models.EventTypeMotion,
		models.EventTypeAlert,
		models.EventTypeMeteor,
	}

	step.Details["event_type"] = rawEvent.EventType
	step.Details["supported_types"] = supportedTypes

	// Check if event type is supported
	isSupported := false
	for _, supportedType := range supportedTypes {
		if rawEvent.EventType == supportedType {
			isSupported = true
			break
		}
	}

	step.Passed = isSupported
	step.Details["is_supported"] = isSupported

	if !isSupported {
		step.Error = fmt.Sprintf("Unsupported event type: %s", rawEvent.EventType)
	}

	return step
}

// validateFile checks basic file information
func (v *MVPValidator) validateFile(rawEvent *models.RawEvent) ValidationStep {
	step := ValidationStep{
		Name:        "file_validation",
		Description: "Validates file information and properties",
		Details:     make(map[string]interface{}),
	}

	issues := []string{}

	// Check file path format (basic validation)
	if len(rawEvent.FilePath) < 3 {
		issues = append(issues, "file_path_too_short")
	}

	// Check file size if provided
	if rawEvent.FileSize != nil {
		step.Details["file_size"] = *rawEvent.FileSize
		if *rawEvent.FileSize <= 0 {
			issues = append(issues, "invalid_file_size")
		}
		// Check for reasonable file size limits (e.g., not more than 100MB for video files)
		if *rawEvent.FileSize > 100*1024*1024 {
			issues = append(issues, "file_size_too_large")
		}
	}

	// Check file type if provided
	if rawEvent.FileType != nil {
		step.Details["file_type"] = *rawEvent.FileType
		// Basic MIME type validation for common formats
		supportedMimeTypes := []string{
			"video/mp4",
			"video/quicktime",
			"video/x-msvideo",
			"image/jpeg",
			"image/png",
			"application/gzip",
			"application/x-tar",
		}
		
		isSupportedMime := false
		for _, mimeType := range supportedMimeTypes {
			if *rawEvent.FileType == mimeType {
				isSupportedMime = true
				break
			}
		}
		
		if !isSupportedMime {
			issues = append(issues, "unsupported_file_type")
		}
		step.Details["supported_mime_types"] = supportedMimeTypes
	}

	step.Details["issues"] = issues
	step.Details["issues_count"] = len(issues)
	step.Passed = len(issues) == 0

	if len(issues) > 0 {
		step.Error = fmt.Sprintf("Found %d file validation issues", len(issues))
	}

	return step
}

// validateMetadata performs basic metadata validation
func (v *MVPValidator) validateMetadata(rawEvent *models.RawEvent) ValidationStep {
	step := ValidationStep{
		Name:        "metadata_validation",
		Description: "Validates event metadata structure and content",
		Details:     make(map[string]interface{}),
	}

	issues := []string{}

	// Check if metadata is valid JSON
	if rawEvent.Metadata != nil {
		var metadata map[string]interface{}
		if err := json.Unmarshal(rawEvent.Metadata, &metadata); err != nil {
			issues = append(issues, "invalid_json_metadata")
			step.Details["json_error"] = err.Error()
		} else {
			step.Details["metadata_keys"] = getKeys(metadata)
			step.Details["metadata_size"] = len(rawEvent.Metadata)
			
			// Check for reasonable metadata size (not more than 10KB)
			if len(rawEvent.Metadata) > 10*1024 {
				issues = append(issues, "metadata_too_large")
			}
		}
	} else {
		// Metadata is optional, so this is not an error
		step.Details["metadata_present"] = false
	}

	step.Details["issues"] = issues
	step.Details["issues_count"] = len(issues)
	step.Passed = len(issues) == 0

	if len(issues) > 0 {
		step.Error = fmt.Sprintf("Found %d metadata validation issues", len(issues))
	}

	return step
}

// generateReason creates a human-readable reason for the validation result
func (v *MVPValidator) generateReason(isValid bool, passedSteps, totalSteps int) string {
	if isValid {
		return fmt.Sprintf("Event passed validation with %d/%d steps completed successfully", passedSteps, totalSteps)
	}
	return fmt.Sprintf("Event failed validation with only %d/%d steps completed successfully (required: 80%%)", passedSteps, totalSteps)
}

// getKeys extracts keys from a map
func getKeys(m map[string]interface{}) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	return keys
}