package config

import (
	"fmt"
	"net"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/joho/godotenv"
	"gopkg.in/yaml.v3"
)

type Config struct {
	Server    ServerConfig    `yaml:"server"`
	Providers ProvidersConfig `yaml:"providers"`
	Storage   StorageConfig   `yaml:"storage"`
	Subagents SubagentsConfig `yaml:"subagents"`
	Auth      AuthConfig      `yaml:"auth"`
	CORS      CORSConfig      `yaml:"cors"`
}

type CORSConfig struct {
	AllowedOrigins []string `yaml:"allowed_origins"`
	AllowedMethods []string `yaml:"allowed_methods"`
	AllowedHeaders []string `yaml:"allowed_headers"`
}

type ServerConfig struct {
	Host     string         `yaml:"host"`
	Port     string         `yaml:"port"`
	Timeouts TimeoutsConfig `yaml:"timeouts"`
	// Legacy fields
	ReadTimeout  time.Duration
	WriteTimeout time.Duration
	IdleTimeout  time.Duration
}

type TimeoutsConfig struct {
	Read  string `yaml:"read"`
	Write string `yaml:"write"`
	Idle  string `yaml:"idle"`
}

type ProvidersConfig struct {
	Anthropic AnthropicProviderConfig `yaml:"anthropic"`
	OpenAI    OpenAIProviderConfig    `yaml:"openai"`
}

type AnthropicProviderConfig struct {
	BaseURL               string        `yaml:"base_url"`
	Version               string        `yaml:"version"`
	MaxRetries            int           `yaml:"max_retries"`
	ResponseHeaderTimeout time.Duration `yaml:"response_header_timeout"`
	DemoteNonstreaming    bool          `yaml:"demote_nonstreaming"`
}

type OpenAIProviderConfig struct {
	BaseURL            string `yaml:"base_url"`
	APIKey             string `yaml:"api_key"`
	AllowClientAPIKey  bool   `yaml:"allow_client_api_key"`  // Allow clients to provide their own API key
	ClientAPIKeyHeader string `yaml:"client_api_key_header"` // Header name for client API key (default: x-openai-api-key)
}

type AuthConfig struct {
	Enabled              bool   `yaml:"enabled"`
	Token                string `yaml:"token"`
	APIKeyHeader         string `yaml:"api_key_header"`
	AllowLocalhostBypass bool   `yaml:"allow_localhost_bypass"`
	DashboardPassword    string `yaml:"dashboard_password"`
	TrustProxy           bool   `yaml:"trust_proxy"` // Skip bind-address auth check (for Docker / reverse-proxy setups)
}

type StorageConfig struct {
	RequestsDir         string   `yaml:"requests_dir"`
	DBType              string   `yaml:"db_type"`
	DBPath              string   `yaml:"db_path"`
	DatabaseURL         string   `yaml:"database_url"`
	CaptureRequestBody  bool     `yaml:"capture_request_body"`
	CaptureResponseBody bool     `yaml:"capture_response_body"`
	MetadataOnly        bool     `yaml:"metadata_only"`
	RetentionDays       int      `yaml:"retention_days"`
	RedactedFields      []string `yaml:"redacted_fields"`
}

type SubagentsConfig struct {
	Enable   bool              `yaml:"enable"`
	Mappings map[string]string `yaml:"mappings"`
}

func Load() (*Config, error) {
	// Load .env file if it exists
	// Look for .env file in the project root (one level up from proxy/)
	envPath := filepath.Join("..", ".env")
	if err := godotenv.Load(envPath); err != nil {
		// If .env doesn't exist in parent directory, try current directory
		if err := godotenv.Load(".env"); err != nil {
			// .env file is optional, so we just log and continue
			// This allows the app to work with system environment variables only
		}
	}

	cfg := defaultConfig()

	if err := loadFirstAvailableConfig(cfg, candidateConfigPaths()); err != nil {
		return nil, err
	}

	// Apply environment variable overrides AFTER loading from file
	if envPort := os.Getenv("PORT"); envPort != "" {
		cfg.Server.Port = envPort
	}
	if envHost := os.Getenv("SERVER_HOST"); envHost != "" {
		cfg.Server.Host = envHost
	}
	if envTimeout := os.Getenv("READ_TIMEOUT"); envTimeout != "" {
		cfg.Server.ReadTimeout = getDuration("READ_TIMEOUT", cfg.Server.ReadTimeout)
	}
	if envTimeout := os.Getenv("WRITE_TIMEOUT"); envTimeout != "" {
		cfg.Server.WriteTimeout = getDuration("WRITE_TIMEOUT", cfg.Server.WriteTimeout)
	}
	if envTimeout := os.Getenv("IDLE_TIMEOUT"); envTimeout != "" {
		cfg.Server.IdleTimeout = getDuration("IDLE_TIMEOUT", cfg.Server.IdleTimeout)
	}

	// Override Anthropic settings
	if envURL := os.Getenv("ANTHROPIC_FORWARD_URL"); envURL != "" {
		cfg.Providers.Anthropic.BaseURL = envURL
	}
	if envVersion := os.Getenv("ANTHROPIC_VERSION"); envVersion != "" {
		cfg.Providers.Anthropic.Version = envVersion
	}
	if envRetries := os.Getenv("ANTHROPIC_MAX_RETRIES"); envRetries != "" {
		cfg.Providers.Anthropic.MaxRetries = getInt("ANTHROPIC_MAX_RETRIES", cfg.Providers.Anthropic.MaxRetries)
	}
	if envTimeout := os.Getenv("ANTHROPIC_RESPONSE_HEADER_TIMEOUT"); envTimeout != "" {
		cfg.Providers.Anthropic.ResponseHeaderTimeout = getDuration("ANTHROPIC_RESPONSE_HEADER_TIMEOUT", cfg.Providers.Anthropic.ResponseHeaderTimeout)
	}
	if os.Getenv("ANTHROPIC_DEMOTE_NONSTREAMING") != "" {
		cfg.Providers.Anthropic.DemoteNonstreaming = envBool("ANTHROPIC_DEMOTE_NONSTREAMING")
	}

	// Override OpenAI settings
	if envURL := os.Getenv("OPENAI_BASE_URL"); envURL != "" {
		cfg.Providers.OpenAI.BaseURL = envURL
	}
	if envKey := os.Getenv("OPENAI_API_KEY"); envKey != "" {
		cfg.Providers.OpenAI.APIKey = envKey
	}
	if os.Getenv("OPENAI_ALLOW_CLIENT_API_KEY") != "" {
		cfg.Providers.OpenAI.AllowClientAPIKey = envBool("OPENAI_ALLOW_CLIENT_API_KEY")
	}
	if envHeader := os.Getenv("OPENAI_CLIENT_API_KEY_HEADER"); envHeader != "" {
		cfg.Providers.OpenAI.ClientAPIKeyHeader = envHeader
	}

	// Override auth settings
	if os.Getenv("AUTH_ENABLED") != "" {
		cfg.Auth.Enabled = envBool("AUTH_ENABLED")
	}
	if envAuthToken := os.Getenv("AUTH_TOKEN"); envAuthToken != "" {
		cfg.Auth.Token = envAuthToken
	}
	if envAPIKeyHeader := os.Getenv("AUTH_API_KEY_HEADER"); envAPIKeyHeader != "" {
		cfg.Auth.APIKeyHeader = envAPIKeyHeader
	}
	if os.Getenv("AUTH_ALLOW_LOCALHOST_BYPASS") != "" {
		cfg.Auth.AllowLocalhostBypass = envBool("AUTH_ALLOW_LOCALHOST_BYPASS")
	}
	if envDashPass := os.Getenv("DASHBOARD_PASSWORD"); envDashPass != "" {
		cfg.Auth.DashboardPassword = envDashPass
	}
	if os.Getenv("TRUST_PROXY") != "" {
		cfg.Auth.TrustProxy = envBool("TRUST_PROXY")
	}

	// Override storage settings
	if envDBType := os.Getenv("DB_TYPE"); envDBType != "" {
		cfg.Storage.DBType = envDBType
	}
	if envPath := os.Getenv("DB_PATH"); envPath != "" {
		cfg.Storage.DBPath = envPath
	}
	if envDatabaseURL := os.Getenv("DATABASE_URL"); envDatabaseURL != "" {
		cfg.Storage.DatabaseURL = envDatabaseURL
	}
	if os.Getenv("STORAGE_CAPTURE_REQUEST_BODY") != "" {
		cfg.Storage.CaptureRequestBody = envBool("STORAGE_CAPTURE_REQUEST_BODY")
	}
	if os.Getenv("STORAGE_CAPTURE_RESPONSE_BODY") != "" {
		cfg.Storage.CaptureResponseBody = envBool("STORAGE_CAPTURE_RESPONSE_BODY")
	}
	if os.Getenv("STORAGE_METADATA_ONLY") != "" {
		cfg.Storage.MetadataOnly = envBool("STORAGE_METADATA_ONLY")
	}
	if envRetentionDays := os.Getenv("STORAGE_RETENTION_DAYS"); envRetentionDays != "" {
		cfg.Storage.RetentionDays = getInt("STORAGE_RETENTION_DAYS", cfg.Storage.RetentionDays)
	}
	if envRedacted := os.Getenv("STORAGE_REDACTED_FIELDS"); envRedacted != "" {
		cfg.Storage.RedactedFields = splitAndTrim(envRedacted)
	}

	if cfg.Storage.MetadataOnly {
		cfg.Storage.CaptureRequestBody = false
		cfg.Storage.CaptureResponseBody = false
	}

	// Override CORS settings (comma-separated values)
	if envOrigins := os.Getenv("CORS_ALLOWED_ORIGINS"); envOrigins != "" {
		cfg.CORS.AllowedOrigins = splitAndTrim(envOrigins)
	}
	if envMethods := os.Getenv("CORS_ALLOWED_METHODS"); envMethods != "" {
		cfg.CORS.AllowedMethods = splitAndTrim(envMethods)
	}
	if envHeaders := os.Getenv("CORS_ALLOWED_HEADERS"); envHeaders != "" {
		cfg.CORS.AllowedHeaders = splitAndTrim(envHeaders)
	}

	// After loading from file, apply any timeout conversions if needed
	if cfg.Server.Timeouts.Read != "" {
		if duration, err := time.ParseDuration(cfg.Server.Timeouts.Read); err == nil {
			cfg.Server.ReadTimeout = duration
		}
	}
	if cfg.Server.Timeouts.Write != "" {
		if duration, err := time.ParseDuration(cfg.Server.Timeouts.Write); err == nil {
			cfg.Server.WriteTimeout = duration
		}
	}
	if cfg.Server.Timeouts.Idle != "" {
		if duration, err := time.ParseDuration(cfg.Server.Timeouts.Idle); err == nil {
			cfg.Server.IdleTimeout = duration
		}
	}

	if err := validateSecurity(cfg); err != nil {
		return nil, err
	}

	return cfg, nil
}

func (c *Config) loadFromFile(path string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return err
	}

	return yaml.Unmarshal(data, c)
}

func defaultConfig() *Config {
	return &Config{
		Server: ServerConfig{
			Host:         "0.0.0.0",
			Port:         "3001",
			ReadTimeout:  600 * time.Second,
			WriteTimeout: 600 * time.Second,
			IdleTimeout:  600 * time.Second,
		},
		Providers: ProvidersConfig{
			Anthropic: AnthropicProviderConfig{
				BaseURL:               "https://api.anthropic.com",
				Version:               "2023-06-01",
				MaxRetries:            3,
				ResponseHeaderTimeout: 300 * time.Second,
			},
			OpenAI: OpenAIProviderConfig{
				BaseURL:            "https://api.openai.com",
				APIKey:             "",
				AllowClientAPIKey:  false,
				ClientAPIKeyHeader: "x-openai-api-key",
			},
		},
		Storage: StorageConfig{
			DBType:              "sqlite",
			DBPath:              "requests.db",
			CaptureRequestBody:  true,
			CaptureResponseBody: true,
			MetadataOnly:        false,
			RetentionDays:       0,
			RedactedFields: []string{
				"api_key",
				"authorization",
				"token",
				"password",
				"secret",
				"access_token",
				"refresh_token",
				"client_secret",
			},
		},
		Subagents: SubagentsConfig{
			Enable:   false,
			Mappings: make(map[string]string),
		},
		Auth: AuthConfig{
			Enabled:              false,
			Token:                "",
			APIKeyHeader:         "x-api-key",
			AllowLocalhostBypass: true,
		},
		CORS: CORSConfig{
			AllowedOrigins: []string{"*"},
			AllowedMethods: []string{"GET", "POST", "DELETE", "OPTIONS"},
			AllowedHeaders: []string{
				"Accept",
				"Authorization",
				"Content-Type",
				"Anthropic-Version",
				"Anthropic-Beta",
				"X-API-Key",
				"X-Requested-With",
			},
		},
	}
}

func candidateConfigPaths() []string {
	paths := []string{
		filepath.Join(filepath.Dir(os.Args[0]), "..", "config.yaml"),
		"config.yaml",
		"../config.yaml",
		"../../config.yaml",
	}

	seen := make(map[string]struct{}, len(paths))
	unique := make([]string, 0, len(paths))
	for _, path := range paths {
		if _, ok := seen[path]; ok {
			continue
		}
		seen[path] = struct{}{}
		unique = append(unique, path)
	}

	return unique
}

func validateSecurity(cfg *Config) error {
	if cfg.Server.Host == "" {
		cfg.Server.Host = "0.0.0.0"
	}

	// When behind a reverse proxy (Docker/Traefik), skip the bind-address auth requirement.
	// The proxy is not directly exposed; the reverse proxy handles access control.
	if cfg.Auth.TrustProxy {
		return nil
	}

	if !isLoopbackHost(cfg.Server.Host) && !cfg.Auth.Enabled {
		return fmt.Errorf("refusing to bind to %q without auth enabled; set AUTH_ENABLED=true and AUTH_TOKEN, or TRUST_PROXY=true for reverse-proxy setups", cfg.Server.Host)
	}

	if cfg.Auth.Enabled && cfg.Auth.Token == "" && !isLoopbackHost(cfg.Server.Host) {
		return fmt.Errorf("auth is enabled for public access but AUTH_TOKEN is empty")
	}

	return nil
}

func isLoopbackHost(host string) bool {
	host = strings.TrimSpace(host)
	if host == "localhost" {
		return true
	}

	if ip := net.ParseIP(strings.Trim(host, "[]")); ip != nil {
		return ip.IsLoopback()
	}

	return false
}

func loadFirstAvailableConfig(cfg *Config, paths []string) error {
	for _, path := range paths {
		if _, err := os.Stat(path); err != nil {
			if os.IsNotExist(err) {
				continue
			}
			return fmt.Errorf("failed to stat config file %q: %w", path, err)
		}

		if err := cfg.loadFromFile(path); err != nil {
			return fmt.Errorf("failed to load config file %q: %w", path, err)
		}
		return nil
	}

	return nil
}

func envBool(key string) bool {
	v := strings.ToLower(os.Getenv(key))
	return v == "true" || v == "1" || v == "yes"
}

func getEnv(key, defaultValue string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return defaultValue
}

func getDuration(key string, defaultValue time.Duration) time.Duration {
	value := os.Getenv(key)
	if value == "" {
		return defaultValue
	}

	duration, err := time.ParseDuration(value)
	if err != nil {
		return defaultValue
	}

	return duration
}

func getInt(key string, defaultValue int) int {
	value := os.Getenv(key)
	if value == "" {
		return defaultValue
	}

	intValue, err := strconv.Atoi(value)
	if err != nil {
		return defaultValue
	}

	return intValue
}

func splitAndTrim(s string) []string {
	parts := strings.Split(s, ",")
	result := make([]string, 0, len(parts))
	for _, part := range parts {
		trimmed := strings.TrimSpace(part)
		if trimmed != "" {
			result = append(result, trimmed)
		}
	}
	return result
}