package config

import (
	"fmt"
	"os"
	"strings"
	"time"

	"northwest.io/muxstr/internal/nostr"
	"gopkg.in/yaml.v3"
)

// Config holds all configuration for the relay.
type Config struct {
	Server     ServerConfig     `yaml:"server"`
	Database   DatabaseConfig   `yaml:"database"`
	Auth       AuthConfig       `yaml:"auth"`
	RateLimit  RateLimitConfig  `yaml:"rate_limit"`
	Metrics    MetricsConfig    `yaml:"metrics"`
	Logging    LoggingConfig    `yaml:"logging"`
	Storage    StorageConfig    `yaml:"storage"`
}

// ServerConfig holds server configuration.
type ServerConfig struct {
	GrpcAddr     string        `yaml:"grpc_addr"`
	HttpAddr     string        `yaml:"http_addr"`
	PublicURL    string        `yaml:"public_url"`
	ReadTimeout  time.Duration `yaml:"read_timeout"`
	WriteTimeout time.Duration `yaml:"write_timeout"`
}

// DatabaseConfig holds database configuration.
type DatabaseConfig struct {
	Path string `yaml:"path"`
	// Note: SQLite connection pooling is handled internally in the storage layer.
	// SQLite works best with a single connection due to its single-writer architecture.
}

// AuthConfig holds authentication configuration.
type AuthConfig struct {
	Enabled          bool     `yaml:"enabled"`
	Required         bool     `yaml:"required"`
	TimestampWindow  int64    `yaml:"timestamp_window"`
	AllowedNpubsRead []string `yaml:"allowed_npubs_read"`  // npub format only (bech32) - normalized to hex internally
	AllowedNpubsWrite []string `yaml:"allowed_npubs_write"` // npub format only (bech32) - normalized to hex internally
	SkipMethods      []string `yaml:"skip_methods"`
}

// RateLimitConfig holds rate limiting configuration.
type RateLimitConfig struct {
	Enabled         bool                       `yaml:"enabled"`
	DefaultRPS      float64                    `yaml:"default_rps"`
	DefaultBurst    int                        `yaml:"default_burst"`
	IPRPS           float64                    `yaml:"ip_rps"`
	IPBurst         int                        `yaml:"ip_burst"`
	Methods         map[string]MethodLimit     `yaml:"methods"`
	Users           map[string]UserLimit       `yaml:"users"`
	SkipMethods     []string                   `yaml:"skip_methods"`
	SkipUsers       []string                   `yaml:"skip_users"`
	CleanupInterval time.Duration              `yaml:"cleanup_interval"`
	MaxIdleTime     time.Duration              `yaml:"max_idle_time"`
}

// MethodLimit defines rate limits for a specific method.
type MethodLimit struct {
	RPS   float64 `yaml:"rps"`
	Burst int     `yaml:"burst"`
}

// UserLimit defines rate limits for a specific user.
type UserLimit struct {
	RPS     float64                `yaml:"rps"`
	Burst   int                    `yaml:"burst"`
	Methods map[string]MethodLimit `yaml:"methods"`
}

// MetricsConfig holds metrics configuration.
type MetricsConfig struct {
	Enabled   bool   `yaml:"enabled"`
	Addr      string `yaml:"addr"`
	Path      string `yaml:"path"`
	Namespace string `yaml:"namespace"`
	Subsystem string `yaml:"subsystem"`
}

// LoggingConfig holds logging configuration.
type LoggingConfig struct {
	Level  string `yaml:"level"`
	Format string `yaml:"format"`
	Output string `yaml:"output"`
}

// StorageConfig holds storage configuration.
type StorageConfig struct {
	AutoCompact     bool          `yaml:"auto_compact"`
	CompactInterval time.Duration `yaml:"compact_interval"`
	MaxEventAge     time.Duration `yaml:"max_event_age"`
}

// Default returns the default configuration.
func Default() *Config {
	return &Config{
		Server: ServerConfig{
			GrpcAddr:     ":50051",
			HttpAddr:     ":8080",
			ReadTimeout:  30 * time.Second,
			WriteTimeout: 30 * time.Second,
		},
		Database: DatabaseConfig{
			Path: "relay.db",
		},
		Auth: AuthConfig{
			Enabled:         false,
			Required:        false,
			TimestampWindow: 60,
		},
		RateLimit: RateLimitConfig{
			Enabled:         false,
			DefaultRPS:      10,
			DefaultBurst:    20,
			IPRPS:           5,
			IPBurst:         10,
			CleanupInterval: 5 * time.Minute,
			MaxIdleTime:     10 * time.Minute,
		},
		Metrics: MetricsConfig{
			Enabled:   true,
			Addr:      ":9090",
			Path:      "/metrics",
			Namespace: "muxstr",
			Subsystem: "relay",
		},
		Logging: LoggingConfig{
			Level:  "info",
			Format: "json",
			Output: "stdout",
		},
		Storage: StorageConfig{
			AutoCompact:     true,
			CompactInterval: 24 * time.Hour,
			MaxEventAge:     0, // unlimited
		},
	}
}

// Load loads configuration from a YAML file and applies environment variable overrides.
func Load(filename string) (*Config, error) {
	// Start with defaults
	cfg := Default()

	// Read file if provided
	if filename != "" {
		data, err := os.ReadFile(filename)
		if err != nil {
			return nil, fmt.Errorf("failed to read config file: %w", err)
		}

		if err := yaml.Unmarshal(data, cfg); err != nil {
			return nil, fmt.Errorf("failed to parse config file: %w", err)
		}
	}

	// Apply environment variable overrides
	applyEnvOverrides(cfg)

	// Normalize npubs to hex pubkeys
	if err := normalizeNpubs(cfg); err != nil {
		return nil, fmt.Errorf("failed to normalize npubs: %w", err)
	}

	// Validate
	if err := cfg.Validate(); err != nil {
		return nil, fmt.Errorf("invalid configuration: %w", err)
	}

	return cfg, nil
}

// normalizeNpubs converts all npub (bech32) pubkeys to hex format.
// Config only accepts npub format (human-readable), which is converted
// to hex format (computer-readable) for internal use.
func normalizeNpubs(cfg *Config) error {
	var err error

	// Normalize read allowlist
	cfg.Auth.AllowedNpubsRead, err = normalizeNpubList(cfg.Auth.AllowedNpubsRead)
	if err != nil {
		return fmt.Errorf("allowed_npubs_read: %w", err)
	}

	// Normalize write allowlist
	cfg.Auth.AllowedNpubsWrite, err = normalizeNpubList(cfg.Auth.AllowedNpubsWrite)
	if err != nil {
		return fmt.Errorf("allowed_npubs_write: %w", err)
	}

	return nil
}

// normalizeNpubList converts a list of npubs to hex pubkeys.
func normalizeNpubList(npubs []string) ([]string, error) {
	if len(npubs) == 0 {
		return nil, nil
	}

	normalized := make([]string, 0, len(npubs))
	for _, npub := range npubs {
		// Skip empty strings
		npub = strings.TrimSpace(npub)
		if npub == "" {
			continue
		}

		// Validate npub format
		if !strings.HasPrefix(npub, "npub1") {
			return nil, fmt.Errorf("invalid npub format %q: must start with 'npub1'", npub)
		}

		// Parse npub to get hex pubkey
		key, err := nostr.ParsePublicKey(npub)
		if err != nil {
			return nil, fmt.Errorf("invalid npub %q: %w", npub, err)
		}

		// Get the hex representation for internal use
		normalized = append(normalized, key.Public())
	}

	return normalized, nil
}

// Validate validates the configuration.
func (c *Config) Validate() error {
	// Validate server addresses
	if c.Server.GrpcAddr == "" {
		return fmt.Errorf("server.grpc_addr is required")
	}
	if c.Server.HttpAddr == "" {
		return fmt.Errorf("server.http_addr is required")
	}

	// Validate database path
	if c.Database.Path == "" {
		return fmt.Errorf("database.path is required")
	}

	// Validate metrics config if enabled
	if c.Metrics.Enabled {
		if c.Metrics.Addr == "" {
			return fmt.Errorf("metrics.addr is required when metrics enabled")
		}
		if c.Metrics.Namespace == "" {
			return fmt.Errorf("metrics.namespace is required when metrics enabled")
		}
	}

	// Validate logging
	validLevels := map[string]bool{"debug": true, "info": true, "warn": true, "error": true}
	if !validLevels[c.Logging.Level] {
		return fmt.Errorf("invalid logging.level: %s (must be debug, info, warn, or error)", c.Logging.Level)
	}

	validFormats := map[string]bool{"json": true, "text": true}
	if !validFormats[c.Logging.Format] {
		return fmt.Errorf("invalid logging.format: %s (must be json or text)", c.Logging.Format)
	}

	return nil
}

// applyEnvOverrides applies environment variable overrides to the configuration.
// Environment variables follow the pattern: MUXSTR_<SECTION>_<KEY>
func applyEnvOverrides(cfg *Config) {
	// Server
	if val := os.Getenv("MUXSTR_SERVER_GRPC_ADDR"); val != "" {
		cfg.Server.GrpcAddr = val
	}
	if val := os.Getenv("MUXSTR_SERVER_HTTP_ADDR"); val != "" {
		cfg.Server.HttpAddr = val
	}
	if val := os.Getenv("MUXSTR_SERVER_PUBLIC_URL"); val != "" {
		cfg.Server.PublicURL = val
	}
	if val := os.Getenv("MUXSTR_SERVER_READ_TIMEOUT"); val != "" {
		if d, err := time.ParseDuration(val); err == nil {
			cfg.Server.ReadTimeout = d
		}
	}
	if val := os.Getenv("MUXSTR_SERVER_WRITE_TIMEOUT"); val != "" {
		if d, err := time.ParseDuration(val); err == nil {
			cfg.Server.WriteTimeout = d
		}
	}

	// Database
	if val := os.Getenv("MUXSTR_DATABASE_PATH"); val != "" {
		cfg.Database.Path = val
	}

	// Auth
	if val := os.Getenv("MUXSTR_AUTH_ENABLED"); val != "" {
		cfg.Auth.Enabled = parseBool(val)
	}
	if val := os.Getenv("MUXSTR_AUTH_REQUIRED"); val != "" {
		cfg.Auth.Required = parseBool(val)
	}
	if val := os.Getenv("MUXSTR_AUTH_TIMESTAMP_WINDOW"); val != "" {
		var n int64
		if _, err := fmt.Sscanf(val, "%d", &n); err == nil {
			cfg.Auth.TimestampWindow = n
		}
	}
	if val := os.Getenv("MUXSTR_AUTH_ALLOWED_NPUBS_READ"); val != "" {
		cfg.Auth.AllowedNpubsRead = strings.Split(val, ",")
	}
	if val := os.Getenv("MUXSTR_AUTH_ALLOWED_NPUBS_WRITE"); val != "" {
		cfg.Auth.AllowedNpubsWrite = strings.Split(val, ",")
	}

	// Rate limit
	if val := os.Getenv("MUXSTR_RATE_LIMIT_ENABLED"); val != "" {
		cfg.RateLimit.Enabled = parseBool(val)
	}
	if val := os.Getenv("MUXSTR_RATE_LIMIT_DEFAULT_RPS"); val != "" {
		var n float64
		if _, err := fmt.Sscanf(val, "%f", &n); err == nil {
			cfg.RateLimit.DefaultRPS = n
		}
	}
	if val := os.Getenv("MUXSTR_RATE_LIMIT_DEFAULT_BURST"); val != "" {
		var n int
		if _, err := fmt.Sscanf(val, "%d", &n); err == nil {
			cfg.RateLimit.DefaultBurst = n
		}
	}

	// Metrics
	if val := os.Getenv("MUXSTR_METRICS_ENABLED"); val != "" {
		cfg.Metrics.Enabled = parseBool(val)
	}
	if val := os.Getenv("MUXSTR_METRICS_ADDR"); val != "" {
		cfg.Metrics.Addr = val
	}
	if val := os.Getenv("MUXSTR_METRICS_PATH"); val != "" {
		cfg.Metrics.Path = val
	}

	// Logging
	if val := os.Getenv("MUXSTR_LOGGING_LEVEL"); val != "" {
		cfg.Logging.Level = val
	}
	if val := os.Getenv("MUXSTR_LOGGING_FORMAT"); val != "" {
		cfg.Logging.Format = val
	}
	if val := os.Getenv("MUXSTR_LOGGING_OUTPUT"); val != "" {
		cfg.Logging.Output = val
	}
}

// parseBool parses a boolean from a string.
func parseBool(s string) bool {
	s = strings.ToLower(s)
	return s == "true" || s == "1" || s == "yes" || s == "on"
}

// Save saves the configuration to a YAML file.
func (c *Config) Save(filename string) error {
	data, err := yaml.Marshal(c)
	if err != nil {
		return fmt.Errorf("failed to marshal config: %w", err)
	}

	if err := os.WriteFile(filename, data, 0644); err != nil {
		return fmt.Errorf("failed to write config file: %w", err)
	}

	return nil
}