package main

import (
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"github.com/seaweedfs/seaweedfs/weed/server/postgres"
	"github.com/seaweedfs/seaweedfs/weed/util"
	flag "github.com/seaweedfs/seaweedfs/weed/util/fla9"
)

const usageLine = "weed-db -port=5432 -master=<master_server>"

const longHelp = `Start a PostgreSQL wire protocol compatible database server that provides SQL query access to SeaweedFS.

This database server enables any PostgreSQL client, tool, or application to connect to SeaweedFS
and execute SQL queries against MQ topics. It implements the PostgreSQL wire protocol for maximum
compatibility with the existing PostgreSQL ecosystem.

Examples:

	# Start database server on default port 5432
	weed-db
	
	# Start with MD5 authentication using JSON format (recommended)
	weed-db -auth=md5 -users='{"admin":"secret","readonly":"view123"}'
	
	# Start with complex passwords using JSON format
	weed-db -auth=md5 -users='{"admin":"pass;with;semicolons","user":"password:with:colons"}'
	
	# Start with credentials from JSON file (most secure)
	weed-db -auth=md5 -users="@/etc/seaweedfs/users.json"
	
	# Start with custom port and master
	weed-db -port=5433 -master=master1:9333
	
	# Allow connections from any host
	weed-db -host=0.0.0.0 -port=5432
	
	# Start with TLS encryption
	weed-db -tls-cert=server.crt -tls-key=server.key

Client Connection Examples:

	# psql command line client
	psql "host=localhost port=5432 dbname=default user=seaweedfs"
	psql -h localhost -p 5432 -U seaweedfs -d default
	
	# With password
	PGPASSWORD=secret psql -h localhost -p 5432 -U admin -d default
	
	# Connection string
	psql "postgresql://admin:secret@localhost:5432/default"

Programming Language Examples:

	# Python (psycopg2)
	import psycopg2
	conn = psycopg2.connect(
		host="localhost", port=5432,
		user="seaweedfs", database="default"
	)
	
	# Java JDBC
	String url = "jdbc:postgresql://localhost:5432/default";
	Connection conn = DriverManager.getConnection(url, "seaweedfs", "");
	
	# Go (lib/pq)
	db, err := sql.Open("postgres", "host=localhost port=5432 user=seaweedfs dbname=default sslmode=disable")
	
	# Node.js (pg)
	const client = new Client({
		host: 'localhost', port: 5432,
		user: 'seaweedfs', database: 'default'
	});

Supported SQL Operations:
	- SELECT queries on MQ topics
	- DESCRIBE/DESC table_name commands
	- EXPLAIN query execution plans
	- SHOW DATABASES/TABLES commands
	- Aggregation functions (COUNT, SUM, AVG, MIN, MAX)
	- WHERE clauses with filtering
	- System columns (_timestamp_ns, _key, _source)
	- Basic PostgreSQL system queries (version(), current_database(), current_user)

Authentication Methods:
	- trust: No authentication required (default)
	- password: Clear text password authentication
	- md5: MD5 password authentication

User Credential Formats:
	- JSON format: '{"user1":"pass1","user2":"pass2"}' (supports any special characters)
	- File format: "@/path/to/users.json" (JSON file)
	
	Note: JSON format supports passwords with semicolons, colons, and any other special characters.
	      File format is recommended for production to keep credentials secure.

Compatible Tools:
	- psql (PostgreSQL command line client)
	- Any PostgreSQL JDBC/ODBC compatible tool

Security Features:
	- Multiple authentication methods
	- TLS encryption support
	- Read-only access (no data modification)

Performance Features:
	- Fast path aggregation optimization (COUNT, MIN, MAX without WHERE clauses)
	- Hybrid data scanning (parquet files + live logs)
	- PostgreSQL wire protocol
	- Query result streaming

`

type Options struct {
	Host        string
	Port        int
	MasterAddr  string
	AuthMethod  string
	Users       string
	Database    string
	MaxConns    int
	IdleTimeout string
	TLSCert     string
	TLSKey      string
}

// Run executes the weed-db CLI.
func Run(args []string) int {
	fs := flag.NewFlagSet("weed-db", flag.ContinueOnError)
	usageWriter := io.Writer(os.Stderr)
	fs.SetOutput(usageWriter)

	var opts Options
	fs.StringVar(&opts.Host, "host", "localhost", "Database server host")
	fs.IntVar(&opts.Port, "port", 5432, "Database server port")
	fs.StringVar(&opts.MasterAddr, "master", "localhost:9333", "SeaweedFS master server address")
	fs.StringVar(&opts.AuthMethod, "auth", "trust", "Authentication method: trust, password, md5")
	fs.StringVar(&opts.Users, "users", "", "User credentials for auth (JSON format '{\"user1\":\"pass1\",\"user2\":\"pass2\"}' or file '@/path/to/users.json')")
	fs.StringVar(&opts.Database, "database", "default", "Default database name")
	fs.IntVar(&opts.MaxConns, "max-connections", 100, "Maximum concurrent connections per server")
	fs.StringVar(&opts.IdleTimeout, "idle-timeout", "1h", "Connection idle timeout")
	fs.StringVar(&opts.TLSCert, "tls-cert", "", "TLS certificate file path")
	fs.StringVar(&opts.TLSKey, "tls-key", "", "TLS private key file path")

	fs.Usage = func() {
		fmt.Fprintf(usageWriter, "Usage: %s\n\n%s\n", usageLine, longHelp)
		fmt.Fprintln(usageWriter, "Default Parameters:")
		fs.PrintDefaults()
	}

	if err := fs.Parse(args); err != nil {
		return 2
	}

	if !runWithOptions(&opts) {
		return 1
	}
	return 0
}

func runWithOptions(opts *Options) bool {
	util.LoadConfiguration("security", false)

	// Validate options.
	if opts.MasterAddr == "" {
		fmt.Fprintf(os.Stderr, "Error: master address is required\n")
		return false
	}

	// Parse authentication method.
	authMethod, err := parseAuthMethod(opts.AuthMethod)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		return false
	}

	// Parse user credentials.
	users, err := parseUsers(opts.Users, authMethod)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		return false
	}

	// Parse idle timeout.
	idleTimeout, err := time.ParseDuration(opts.IdleTimeout)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error parsing idle timeout: %v\n", err)
		return false
	}

	// Validate port number.
	if err := validatePortNumber(opts.Port); err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		return false
	}

	// Setup TLS if requested.
	var tlsConfig *tls.Config
	if opts.TLSCert != "" && opts.TLSKey != "" {
		cert, err := tls.LoadX509KeyPair(opts.TLSCert, opts.TLSKey)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error loading TLS certificates: %v\n", err)
			return false
		}
		tlsConfig = &tls.Config{
			Certificates: []tls.Certificate{cert},
		}
	}

	// Create server configuration.
	config := &postgres.PostgreSQLServerConfig{
		Host:        opts.Host,
		Port:        opts.Port,
		AuthMethod:  authMethod,
		Users:       users,
		Database:    opts.Database,
		MaxConns:    opts.MaxConns,
		IdleTimeout: idleTimeout,
		TLSConfig:   tlsConfig,
	}

	// Create database server.
	dbServer, err := postgres.NewPostgreSQLServer(config, opts.MasterAddr)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error creating database server: %v\n", err)
		return false
	}

	// Print startup information.
	fmt.Printf("Starting SeaweedFS Database Server...\n")
	fmt.Printf("Host: %s\n", opts.Host)
	fmt.Printf("Port: %d\n", opts.Port)
	fmt.Printf("Master: %s\n", opts.MasterAddr)
	fmt.Printf("Database: %s\n", opts.Database)
	fmt.Printf("Auth Method: %s\n", opts.AuthMethod)
	fmt.Printf("Max Connections: %d\n", opts.MaxConns)
	fmt.Printf("Idle Timeout: %s\n", opts.IdleTimeout)
	if tlsConfig != nil {
		fmt.Printf("TLS: Enabled\n")
	} else {
		fmt.Printf("TLS: Disabled\n")
	}
	if len(users) > 0 {
		fmt.Printf("Users: %d configured\n", len(users))
	}

	fmt.Printf("\nDatabase Connection Examples:\n")
	fmt.Printf("  psql -h %s -p %d -U seaweedfs -d %s\n", opts.Host, opts.Port, opts.Database)
	if len(users) > 0 {
		// Show first user as example.
		for username := range users {
			fmt.Printf("  psql -h %s -p %d -U %s -d %s\n", opts.Host, opts.Port, username, opts.Database)
			break
		}
	}
	fmt.Printf("  postgresql://%s:%d/%s\n", opts.Host, opts.Port, opts.Database)

	fmt.Printf("\nSupported Operations:\n")
	fmt.Printf("  - SELECT queries on MQ topics\n")
	fmt.Printf("  - DESCRIBE/DESC table_name\n")
	fmt.Printf("  - EXPLAIN query execution plans\n")
	fmt.Printf("  - SHOW DATABASES/TABLES\n")
	fmt.Printf("  - Aggregations: COUNT, SUM, AVG, MIN, MAX\n")
	fmt.Printf("  - System columns: _timestamp_ns, _key, _source\n")
	fmt.Printf("  - Basic PostgreSQL system queries\n")

	fmt.Printf("\nReady for database connections!\n\n")

	// Start the server.
	err = dbServer.Start()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error starting database server: %v\n", err)
		return false
	}

	// Set up signal handling for graceful shutdown.
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

	// Wait for shutdown signal.
	<-sigChan
	fmt.Printf("\nReceived shutdown signal, stopping database server...\n")

	// Create context with timeout for graceful shutdown.
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	// Stop the server with timeout.
	done := make(chan error, 1)
	go func() {
		done <- dbServer.Stop()
	}()

	select {
	case err := <-done:
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error stopping database server: %v\n", err)
			return false
		}
		fmt.Printf("Database server stopped successfully\n")
	case <-ctx.Done():
		fmt.Fprintf(os.Stderr, "Timeout waiting for database server to stop\n")
		return false
	}

	return true
}

// parseAuthMethod parses the authentication method string.
func parseAuthMethod(method string) (postgres.AuthMethod, error) {
	switch strings.ToLower(method) {
	case "trust":
		return postgres.AuthTrust, nil
	case "password":
		return postgres.AuthPassword, nil
	case "md5":
		return postgres.AuthMD5, nil
	default:
		return postgres.AuthTrust, fmt.Errorf("unsupported auth method '%s'. Supported: trust, password, md5", method)
	}
}

// parseUsers parses the user credentials string with support for secure formats only.
// Supported formats:
// 1. JSON format: {"username":"password","username2":"password2"}
// 2. File format: /path/to/users.json or @/path/to/users.json
func parseUsers(usersStr string, authMethod postgres.AuthMethod) (map[string]string, error) {
	users := make(map[string]string)

	if usersStr == "" {
		// No users specified.
		if authMethod != postgres.AuthTrust {
			return nil, fmt.Errorf("users must be specified when auth method is not 'trust'")
		}
		return users, nil
	}

	// Trim whitespace.
	usersStr = strings.TrimSpace(usersStr)

	// Determine format and parse accordingly.
	if strings.HasPrefix(usersStr, "{") && strings.HasSuffix(usersStr, "}") {
		// JSON format.
		return parseUsersJSON(usersStr, authMethod)
	}

	// Check if it's a file path (with or without @ prefix) before declaring invalid format.
	filePath := strings.TrimPrefix(usersStr, "@")
	if _, err := os.Stat(filePath); err == nil {
		// File format.
		return parseUsersFile(usersStr, authMethod) // Pass original string to preserve @ handling.
	}

	// Invalid format.
	return nil, fmt.Errorf("invalid user credentials format. Use JSON format '{\"user\":\"pass\"}' or file format '@/path/to/users.json' or 'path/to/users.json'. Legacy semicolon-separated format is no longer supported")
}

// parseUsersJSON parses user credentials from JSON format.
func parseUsersJSON(jsonStr string, authMethod postgres.AuthMethod) (map[string]string, error) {
	var users map[string]string
	if err := json.Unmarshal([]byte(jsonStr), &users); err != nil {
		return nil, fmt.Errorf("invalid JSON format for users: %v", err)
	}

	// Validate users.
	for username, password := range users {
		if username == "" {
			return nil, fmt.Errorf("empty username in JSON user specification")
		}
		if authMethod != postgres.AuthTrust && password == "" {
			return nil, fmt.Errorf("empty password for user '%s' with auth method", username)
		}
	}

	return users, nil
}

// parseUsersFile parses user credentials from a JSON file.
func parseUsersFile(filePath string, authMethod postgres.AuthMethod) (map[string]string, error) {
	// Remove @ prefix if present.
	filePath = strings.TrimPrefix(filePath, "@")

	// Read file content.
	content, err := os.ReadFile(filePath)
	if err != nil {
		return nil, fmt.Errorf("failed to read users file '%s': %v", filePath, err)
	}

	contentStr := strings.TrimSpace(string(content))

	// File must contain JSON format.
	if !strings.HasPrefix(contentStr, "{") || !strings.HasSuffix(contentStr, "}") {
		return nil, fmt.Errorf("users file '%s' must contain JSON format: {\"user\":\"pass\"}. Legacy formats are no longer supported", filePath)
	}

	// Parse as JSON.
	return parseUsersJSON(contentStr, authMethod)
}

// validatePortNumber validates that the port number is reasonable.
func validatePortNumber(port int) error {
	if port < 1 || port > 65535 {
		return fmt.Errorf("port number must be between 1 and 65535, got %d", port)
	}
	if port < 1024 {
		fmt.Fprintf(os.Stderr, "Warning: port number %d may require root privileges\n", port)
	}
	return nil
}
