package fetchguard

import (
	"crypto/tls"
	"fmt"
	"math"
	"time"

	"git.golem15.com/golem15/summercms/modules/compass"
)

// Mode selects host-allow-list vs any-public-host. The private/loopback/
// reserved IP block is always on regardless of Mode (D-11).
type Mode int

const (
	AllowHostsMode Mode = iota
	PublicOnlyMode
)

// Reason is the closed set of Fetch failure reasons, matching PHP's
// invalid_url/scheme/unresolvable/private_ip/network_error/too_large family.
type Reason string

const (
	ReasonInvalidURL   Reason = "invalid_url"
	ReasonScheme       Reason = "scheme"
	ReasonUnresolvable Reason = "unresolvable"
	ReasonPrivateIP    Reason = "private_ip"
	ReasonNetworkError Reason = "network_error"
	ReasonTooLarge     Reason = "too_large"
)

// Policy is supplied per call.
type Policy struct {
	Mode       Mode
	AllowHosts []string // exact or dotted-suffix match; used in AllowHostsMode
	MaxBytes   int64    // 0 means use the config/framework default, never unlimited
	Timeout    time.Duration

	// tlsConfig, if set, is Transport.TLSClientConfig so tests can trust an
	// httptest certificate. Production callers leave it nil.
	tlsConfig *tls.Config
	// skipReservedCheck disables the dial-time private-IP block so tests can
	// exercise a real httptest listener on 127.0.0.1. Production callers
	// leave it false.
	skipReservedCheck bool
}

// Error carries the typed Reason plus the underlying error for logging.
type Error struct {
	Reason Reason
	Err    error
}

func (e *Error) Error() string {
	if e == nil {
		return "fetchguard: error"
	}
	if e.Err != nil {
		return fmt.Sprintf("fetchguard: %s: %v", e.Reason, e.Err)
	}
	return fmt.Sprintf("fetchguard: %s", e.Reason)
}

func (e *Error) Unwrap() error {
	if e == nil {
		return nil
	}
	return e.Err
}

// Defaults are the framework fallback: 10 MiB, 10s, matching PHP.
func Defaults() (maxBytes int64, timeout time.Duration) {
	return 10 * 1024 * 1024, 10 * time.Second
}

// DefaultsFromConfig reads http.fetch.max_bytes / http.fetch.timeout_seconds
// from cfg, falling back to Defaults() for absent keys. An explicitly
// configured zero or negative value is an error (D-14).
func DefaultsFromConfig(cfg *compass.Config) (maxBytes int64, timeout time.Duration, err error) {
	maxBytes, timeout = Defaults()
	if cfg == nil {
		return maxBytes, timeout, nil
	}
	if v, ok := cfg.Lookup("http.fetch.max_bytes"); ok {
		n, err := configInt64("http.fetch.max_bytes", v)
		if err != nil {
			return 0, 0, err
		}
		if n <= 0 {
			return 0, 0, fmt.Errorf("fetchguard: http.fetch.max_bytes must be positive, got %d", n)
		}
		maxBytes = n
	}
	if v, ok := cfg.Lookup("http.fetch.timeout_seconds"); ok {
		n, err := configInt64("http.fetch.timeout_seconds", v)
		if err != nil {
			return 0, 0, err
		}
		if n <= 0 {
			return 0, 0, fmt.Errorf("fetchguard: http.fetch.timeout_seconds must be positive, got %d", n)
		}
		timeout = time.Duration(n) * time.Second
	}
	return maxBytes, timeout, nil
}

func configInt64(path string, v any) (int64, error) {
	switch n := v.(type) {
	case int:
		return int64(n), nil
	case int8:
		return int64(n), nil
	case int16:
		return int64(n), nil
	case int32:
		return int64(n), nil
	case int64:
		return n, nil
	case uint:
		return int64(n), nil
	case uint8:
		return int64(n), nil
	case uint16:
		return int64(n), nil
	case uint32:
		return int64(n), nil
	case uint64:
		if n > math.MaxInt64 {
			return 0, fmt.Errorf("fetchguard: %s overflows int64", path)
		}
		return int64(n), nil
	case float64:
		if math.Trunc(n) != n {
			return 0, fmt.Errorf("fetchguard: %s is not an integer", path)
		}
		if n > math.MaxInt64 || n < math.MinInt64 {
			return 0, fmt.Errorf("fetchguard: %s overflows int64", path)
		}
		return int64(n), nil
	case float32:
		return configInt64(path, float64(n))
	default:
		return 0, fmt.Errorf("fetchguard: %s has unexpected type %T", path, v)
	}
}