// Package config owns GL configuration loading and validation.
package config

import (
	"fmt"
	"time"

	"github.com/knadh/koanf/parsers/toml"
	"github.com/knadh/koanf/providers/file"
	"github.com/knadh/koanf/v2"
)

type Config struct {
	Environment string         `koanf:"environment"`
	GRPC        GRPCConfig     `koanf:"grpc"`
	Database    DatabaseConfig `koanf:"database"`
}

type GRPCConfig struct {
	Host            string        `koanf:"host"`
	Port            int           `koanf:"port"`
	ShutdownTimeout time.Duration `koanf:"shutdown-timeout"`
}

type DatabaseConfig struct {
	Host     string `koanf:"host"`
	Port     int    `koanf:"port"`
	Name     string `koanf:"name"`
	User     string `koanf:"user"`
	Password string `koanf:"password"`
	SSLMode  string `koanf:"ssl-mode"`
}

func Load(path string) (*Config, error) {
	cfg := &Config{
		Environment: "local",
		GRPC: GRPCConfig{
			Host:            "0.0.0.0",
			Port:            8500,
			ShutdownTimeout: 10 * time.Second,
		},
		Database: DatabaseConfig{
			Host:    "127.0.0.1",
			Port:    5432,
			Name:    "gl_db",
			User:    "postgres",
			SSLMode: "disable",
		},
	}

	k := koanf.New(".")
	if err := k.Load(file.Provider(path), toml.Parser()); err != nil {
		return nil, fmt.Errorf("load config: %w", err)
	}
	if err := k.Unmarshal("", cfg); err != nil {
		return nil, fmt.Errorf("decode config: %w", err)
	}
	if err := cfg.Validate(); err != nil {
		return nil, err
	}
	return cfg, nil
}

func (c *Config) Validate() error {
	if c.GRPC.Host == "" {
		return fmt.Errorf("grpc host is required")
	}
	if c.GRPC.Port < 0 || c.GRPC.Port > 65535 {
		return fmt.Errorf("grpc port must be between 0 and 65535")
	}
	if c.GRPC.ShutdownTimeout <= 0 {
		return fmt.Errorf("grpc shutdown timeout must be positive")
	}
	if c.Database.Host == "" || c.Database.Name == "" || c.Database.User == "" {
		return fmt.Errorf("database host, name, and user are required")
	}
	if c.Database.Port < 1 || c.Database.Port > 65535 {
		return fmt.Errorf("database port must be between 1 and 65535")
	}
	return nil
}