package config

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

	"github.com/pelletier/go-toml/v2"

	mcdslauth "git.wntrmute.dev/mc/mcdsl/auth"
)

// Config is the MCQ configuration.
type Config struct {
	Server   ServerConfig   `toml:"server"`
	Database DatabaseConfig `toml:"database"`
	MCIAS    mcdslauth.Config `toml:"mcias"`
	Log      LogConfig      `toml:"log"`
}

// ServerConfig holds HTTP/gRPC server settings. TLS fields are optional;
// when empty, MCQ serves plain HTTP (for use behind mc-proxy L7).
type ServerConfig struct {
	ListenAddr      string   `toml:"listen_addr"`
	GRPCAddr        string   `toml:"grpc_addr"`
	TLSCert         string   `toml:"tls_cert"`
	TLSKey          string   `toml:"tls_key"`
	ReadTimeout     Duration `toml:"read_timeout"`
	WriteTimeout    Duration `toml:"write_timeout"`
	IdleTimeout     Duration `toml:"idle_timeout"`
	ShutdownTimeout Duration `toml:"shutdown_timeout"`
}

type DatabaseConfig struct {
	Path string `toml:"path"`
}

type LogConfig struct {
	Level string `toml:"level"`
}

// Duration wraps time.Duration for TOML string parsing.
type Duration struct {
	time.Duration
}

func (d *Duration) UnmarshalText(text []byte) error {
	var err error
	d.Duration, err = time.ParseDuration(string(text))
	return err
}

// Load reads, parses, and validates a config file.
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path) // #nosec G304 -- config path is operator-controlled
	if err != nil {
		return nil, fmt.Errorf("read config: %w", err)
	}

	cfg := &Config{
		Server: ServerConfig{
			ListenAddr:   ":8080",
			ReadTimeout:  Duration{30 * time.Second},
			WriteTimeout: Duration{30 * time.Second},
			IdleTimeout:  Duration{120 * time.Second},
			ShutdownTimeout: Duration{60 * time.Second},
		},
		Log: LogConfig{Level: "info"},
	}

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

	applyEnvOverrides(cfg)

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

	return cfg, nil
}

func (c *Config) validate() error {
	if c.Server.ListenAddr == "" {
		return fmt.Errorf("config: server.listen_addr is required")
	}
	if c.Database.Path == "" {
		return fmt.Errorf("config: database.path is required")
	}
	if c.MCIAS.ServerURL == "" {
		return fmt.Errorf("config: mcias.server_url is required")
	}
	return nil
}

func applyEnvOverrides(cfg *Config) {
	if port := os.Getenv("PORT"); port != "" {
		cfg.Server.ListenAddr = ":" + port
	}
	applyEnvToStruct("MCQ", reflect.ValueOf(cfg).Elem())
}

func applyEnvToStruct(prefix string, v reflect.Value) {
	t := v.Type()
	for i := range t.NumField() {
		field := t.Field(i)
		fv := v.Field(i)

		tag := field.Tag.Get("toml")
		if tag == "" || tag == "-" {
			continue
		}

		envKey := prefix + "_" + strings.ToUpper(tag)

		if fv.Kind() == reflect.Struct && field.Type != reflect.TypeOf(Duration{}) {
			applyEnvToStruct(envKey, fv)
			continue
		}

		envVal := os.Getenv(envKey)
		if envVal == "" {
			continue
		}

		if fv.Kind() == reflect.String {
			fv.SetString(envVal)
		}
		if field.Type == reflect.TypeOf(Duration{}) {
			if d, err := time.ParseDuration(envVal); err == nil {
				fv.Set(reflect.ValueOf(Duration{d}))
			}
		}
	}
}