package commands

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/modelcontextprotocol/registry/internal/validators"
	apiv0 "github.com/modelcontextprotocol/registry/pkg/api/v0"
	"github.com/modelcontextprotocol/registry/pkg/model"
)

// printSchemaValidationErrors prints nicely formatted error messages for schema validation issues
// (empty schema or non-current schema) with migration guidance to stdout.
// Returns the formatted error message string if any schema errors were printed, empty string otherwise.
func printSchemaValidationErrors(result *validators.ValidationResult, serverJSON *apiv0.ServerJSON) string {
	currentSchemaURL := model.CurrentSchemaURL
	migrationURL := "https://github.com/modelcontextprotocol/registry/blob/main/docs/reference/server-json/CHANGELOG.md"
	checklistURL := migrationURL + "#migration-checklist-for-publishers"

	var formattedMsg strings.Builder

	for _, issue := range result.Issues {
		switch issue.Reference {
		case "schema-field-required":
			// Empty/missing schema
			_, _ = fmt.Fprintf(os.Stdout, "$schema field is required.\n")
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintf(os.Stdout, "Expected current schema: %s\n", currentSchemaURL)
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintln(os.Stdout, "Run 'mcp-publisher init' to create a new server.json with the correct schema, or update your existing server.json file.")
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintf(os.Stdout, "📋 Migration checklist: %s\n", checklistURL)
			_, _ = fmt.Fprintf(os.Stdout, "📖 Full changelog with examples: %s\n", migrationURL)
			_, _ = fmt.Fprintln(os.Stdout)

			// Build formatted error message
			_, _ = fmt.Fprintf(&formattedMsg, "$schema field is required. Expected current schema: %s. 📋 Migration checklist: %s 📖 Full changelog with examples: %s", currentSchemaURL, checklistURL, migrationURL)
			return formattedMsg.String() // Only one schema error at a time

		case "schema-version-deprecated":
			// Non-current schema
			if issue.Severity == validators.ValidationIssueSeverityWarning {
				// Warning format (for validate command)
				_, _ = fmt.Fprintf(os.Stdout, "⚠️  Deprecated schema detected: %s\n", serverJSON.Schema)
			} else {
				// Error format (for publish command)
				_, _ = fmt.Fprintf(os.Stdout, "deprecated schema detected: %s.\n", serverJSON.Schema)
			}
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintf(os.Stdout, "Expected current schema: %s\n", currentSchemaURL)
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintln(os.Stdout, "Migrate to the current schema format for new servers.")
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintf(os.Stdout, "📋 Migration checklist: %s\n", checklistURL)
			_, _ = fmt.Fprintf(os.Stdout, "📖 Full changelog with examples: %s\n", migrationURL)
			_, _ = fmt.Fprintln(os.Stdout)

			// Build formatted error message - include the original issue message for test compatibility
			_, _ = fmt.Fprintf(&formattedMsg, "%s. deprecated schema detected: %s. Expected current schema: %s. Migrate to the current schema format for new servers. 📋 Migration checklist: %s 📖 Full changelog with examples: %s", issue.Message, serverJSON.Schema, currentSchemaURL, checklistURL, migrationURL)
			return formattedMsg.String() // Only one schema error at a time

		case "schema-version-extraction-error":
			// Invalid schema URL format - also include migration links for consistency
			// Build formatted error message with migration links
			_, _ = fmt.Fprintf(&formattedMsg, "%s. 📋 Migration checklist: %s 📖 Full changelog with examples: %s", issue.Message, checklistURL, migrationURL)
			return formattedMsg.String()
		}
	}

	return ""
}

// printValidationIssues prints schema validation errors and all other validation issues.
// Returns the formatted error message string for schema validation errors (empty string if none).
func printValidationIssues(result *validators.ValidationResult, serverJSON *apiv0.ServerJSON) string {
	// Print schema validation errors/warnings with friendly messages
	formattedErrorMsg := printSchemaValidationErrors(result, serverJSON)

	if result.Valid {
		return formattedErrorMsg
	}

	// Print all issues
	_, _ = fmt.Fprintf(os.Stdout, "❌ Validation failed with %d issue(s):\n", len(result.Issues))
	_, _ = fmt.Fprintln(os.Stdout)

	// Track which schema issues we've already printed to avoid duplicates
	issueNum := 1

	for _, issue := range result.Issues {
		// Skip schema issues that were already printed (they're printed by printSchemaValidationErrors above)
		if issue.Reference == "schema-field-required" || issue.Reference == "schema-version-deprecated" {
			continue
		}

		// Print other issues normally
		_, _ = fmt.Fprintf(os.Stdout, "%d. [%s] %s (%s)\n", issueNum, issue.Severity, issue.Path, issue.Type)
		_, _ = fmt.Fprintf(os.Stdout, "   %s\n", issue.Message)
		if issue.Reference != "" {
			_, _ = fmt.Fprintf(os.Stdout, "   Reference: %s\n", issue.Reference)
		}
		_, _ = fmt.Fprintln(os.Stdout)
		issueNum++
	}

	return formattedErrorMsg
}

func ValidateCommand(args []string) error {
	// Parse arguments
	serverFile := "server.json"

	for _, arg := range args {
		if arg == "--help" || arg == "-h" {
			_, _ = fmt.Fprintln(os.Stdout, "Usage: mcp-publisher validate [file]")
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintln(os.Stdout, "Validate a server.json file without publishing.")
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintln(os.Stdout, "Arguments:")
			_, _ = fmt.Fprintln(os.Stdout, "  file    Path to server.json file (default: ./server.json)")
			_, _ = fmt.Fprintln(os.Stdout)
			_, _ = fmt.Fprintln(os.Stdout, "The validate command performs exhaustive validation, reporting all issues at once.")
			_, _ = fmt.Fprintln(os.Stdout, "It validates JSON syntax, schema compliance, and semantic rules.")
			return nil
		}
		if !strings.HasPrefix(arg, "-") {
			serverFile = arg
		}
	}

	// Read server file
	serverData, err := os.ReadFile(serverFile)
	if err != nil {
		if os.IsNotExist(err) {
			return fmt.Errorf("%s not found, please check the file path", serverFile)
		}
		return fmt.Errorf("failed to read %s: %w", serverFile, err)
	}

	// Validate JSON
	var serverJSON apiv0.ServerJSON
	if err := json.Unmarshal(serverData, &serverJSON); err != nil {
		return fmt.Errorf("invalid JSON: %w", err)
	}

	// Get registry URL (same pattern as publish)
	homeDir, err := os.UserHomeDir()
	if err != nil {
		return fmt.Errorf("failed to get home directory: %w", err)
	}

	tokenPath := filepath.Join(homeDir, TokenFileName)
	registryURL := DefaultRegistryURL
	// Try to read registry URL from token file (if it exists)
	if tokenData, err := os.ReadFile(tokenPath); err == nil {
		var tokenInfo map[string]string
		if err := json.Unmarshal(tokenData, &tokenInfo); err == nil {
			if url := tokenInfo["registry"]; url != "" {
				registryURL = url
			}
		}
	}

	// Validate via API
	_, _ = fmt.Fprintf(os.Stdout, "Validating against %s...\n", registryURL)
	result, err := validateViaAPI(registryURL, serverData)
	if err != nil {
		return fmt.Errorf("validation failed: %w", err)
	}

	// Print validation results using shared formatting logic
	formattedErrorMsg := printValidationIssues(result, &serverJSON)

	if result.Valid {
		_, _ = fmt.Fprintln(os.Stdout, "✅ server.json is valid")
		return nil
	}

	// Return error with formatted message if available
	if formattedErrorMsg != "" {
		return fmt.Errorf("%s", formattedErrorMsg)
	}

	return fmt.Errorf("validation failed")
}

// validateViaAPI calls the /validate endpoint on the registry
func validateViaAPI(registryURL string, serverData []byte) (*validators.ValidationResult, error) {
	// Parse the server JSON data to ensure it's valid JSON
	var serverJSON apiv0.ServerJSON
	err := json.Unmarshal(serverData, &serverJSON)
	if err != nil {
		return nil, fmt.Errorf("error parsing server.json file: %w", err)
	}

	// Convert to JSON
	jsonData, err := json.Marshal(serverJSON)
	if err != nil {
		return nil, fmt.Errorf("error serializing request: %w", err)
	}

	// Ensure URL ends with / and add validate endpoint
	if !strings.HasSuffix(registryURL, "/") {
		registryURL += "/"
	}
	validateURL := registryURL + "v0/validate"

	// Create and send request
	req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, validateURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("error creating request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("error sending request: %w", err)
	}
	defer resp.Body.Close()

	// Read response
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("error reading response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("server returned status %d: %s", resp.StatusCode, body)
	}

	// Parse response - Huma returns ValidationResult directly
	var result validators.ValidationResult
	if err := json.Unmarshal(body, &result); err != nil {
		return nil, fmt.Errorf("error parsing response: %w", err)
	}

	return &result, nil
}