// Package config handles configuration loading and validation.
package config

import (
	"fmt"
	"net"
	"os"
	"strings"

	"github.com/BurntSushi/toml"
)

// Config holds the complete application configuration.
type Config struct {
	Matrix MatrixConfig `toml:"matrix"`
}

// MatrixConfig holds Matrix-native bot settings.
type MatrixConfig struct {
	Shadow         bool     `toml:"shadow"`         // Shadow mode (log only)
	HealthAddr     string   `toml:"healthAddr"`     // Health server listen address
	Server         string   `toml:"server"`         // Homeserver base URL
	AccessToken    string   `toml:"accessToken"`    // Access token for bot user
	UserID         string   `toml:"userId"`         // Full Matrix user ID
	Rooms          []string `toml:"rooms"`          // Allowlisted room IDs
	StateStorePath string   `toml:"stateStorePath"` // Path to state store (sync token/dedupe)
}

// Load reads and parses a TOML configuration file.
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading config file: %w", err)
	}

	var cfg Config
	if err := toml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parsing config file: %w", err)
	}

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

	return &cfg, nil
}

// Validate checks that required configuration fields are set.
func (c *Config) Validate() error {
	if c.Matrix.Server == "" {
		return fmt.Errorf("matrix.server is required")
	}
	if c.Matrix.AccessToken == "" {
		return fmt.Errorf("matrix.accessToken is required")
	}
	if c.Matrix.UserID == "" {
		return fmt.Errorf("matrix.userId is required")
	}
	if len(c.Matrix.Rooms) == 0 {
		return fmt.Errorf("matrix.rooms must include at least one room")
	}
	if c.Matrix.StateStorePath == "" {
		c.Matrix.StateStorePath = "data/matrix-state.db"
	}
	if c.Matrix.HealthAddr != "" {
		if err := validateLocalHealthAddr(c.Matrix.HealthAddr); err != nil {
			return err
		}
	}
	return nil
}

func validateLocalHealthAddr(addr string) error {
	host, _, err := net.SplitHostPort(addr)
	if err != nil {
		return fmt.Errorf("matrix.healthAddr must be host:port: %w", err)
	}
	if host == "" {
		return fmt.Errorf("matrix.healthAddr must bind to localhost (use 127.0.0.1:PORT)")
	}
	normalized := strings.ToLower(host)
	if normalized == "localhost" || normalized == "127.0.0.1" || normalized == "::1" {
		return nil
	}
	return fmt.Errorf("matrix.healthAddr must bind to localhost (got %s)", host)
}