//go:build windows

package starssh

import (
	"context"
	"errors"
	"net"
	"os"
	"strings"
	"time"

	"github.com/Microsoft/go-winio"
	"golang.org/x/sys/windows"
)

const defaultWindowsSSHAgentPipe = `\\.\pipe\openssh-ssh-agent`

func dialSSHAgent(timeout time.Duration) (net.Conn, error) {
	agentSock := strings.TrimSpace(os.Getenv("SSH_AUTH_SOCK"))
	if agentSock != "" {
		return dialWindowsSSHAgentEndpoint(agentSock, timeout)
	}
	return dialWindowsNamedPipe(defaultWindowsSSHAgentPipe, timeout, true)
}

func dialWindowsSSHAgentEndpoint(endpoint string, timeout time.Duration) (net.Conn, error) {
	if pipePath, ok := normalizeWindowsSSHAgentPipe(endpoint); ok {
		return dialWindowsNamedPipe(pipePath, timeout, false)
	}
	if timeout > 0 {
		return net.DialTimeout("unix", endpoint, timeout)
	}
	return net.Dial("unix", endpoint)
}

func dialWindowsNamedPipe(path string, timeout time.Duration, unavailableOnNotFound bool) (net.Conn, error) {
	ctx := context.Background()
	cancel := func() {}
	if timeout > 0 {
		ctx, cancel = context.WithTimeout(ctx, timeout)
	}
	defer cancel()

	conn, err := winio.DialPipeContext(ctx, path)
	if err != nil && unavailableOnNotFound && isWindowsPipeUnavailable(err) {
		return nil, errSSHAgentUnavailable
	}
	return conn, err
}

func normalizeWindowsSSHAgentPipe(endpoint string) (string, bool) {
	trimmed := strings.TrimSpace(endpoint)
	if trimmed == "" {
		return "", false
	}

	normalized := trimmed
	if strings.HasPrefix(normalized, "//./pipe/") {
		normalized = `\\.\pipe\` + strings.TrimPrefix(normalized, "//./pipe/")
	}
	if strings.HasPrefix(normalized, `\\.\pipe\`) {
		return normalized, true
	}
	return "", false
}

func isWindowsPipeUnavailable(err error) bool {
	return errors.Is(err, windows.ERROR_FILE_NOT_FOUND) || errors.Is(err, windows.ERROR_PATH_NOT_FOUND)
}