package main

import (
	"context"
	"errors"
	"io"
	"log"
	"net"
	"os"
	"sync"
	"testing"
	"time"

	"hakurei.app/check"
	"hakurei.app/internal/pkg"
)

// daemonTimeout is the maximum amount of time cureFromIR will wait on I/O.
const daemonTimeout = 30 * time.Second

// daemonDeadline returns the deadline corresponding to daemonTimeout, or the
// zero value when running in a test.
func daemonDeadline() time.Time {
	if testing.Testing() {
		return time.Time{}
	}
	return time.Now().Add(daemonTimeout)
}

// cureFromIR services an IR curing request.
func cureFromIR(
	ctx context.Context,
	cache *pkg.Cache,
	conn net.Conn,
) (pkg.Artifact, error) {
	go func() {
		<-ctx.Done()
		_ = conn.SetDeadline(time.Now())
	}()

	if err := conn.SetReadDeadline(daemonDeadline()); err != nil {
		return nil, errors.Join(err, conn.Close())
	}

	a, decodeErr := cache.NewDecoder(conn).Decode()
	if decodeErr != nil {
		_, err := conn.Write([]byte("\x00" + decodeErr.Error()))
		return nil, errors.Join(decodeErr, err, conn.Close())
	}

	pathname, _, cureErr := cache.Cure(a)
	if err := conn.SetWriteDeadline(daemonDeadline()); err != nil {
		if !testing.Testing() || !errors.Is(err, io.ErrClosedPipe) {
			return a, errors.Join(err, conn.Close())
		}
	}
	if cureErr != nil {
		_, err := conn.Write([]byte("\x00" + cureErr.Error()))
		return a, errors.Join(cureErr, err, conn.Close())
	}
	_, err := conn.Write([]byte(pathname.String()))
	if testing.Testing() && errors.Is(err, io.ErrClosedPipe) {
		return a, nil
	}
	return a, errors.Join(err, conn.Close())
}

// serve services connections from a [net.UnixListener].
func serve(ctx context.Context, log *log.Logger, cm *cache, ul *net.UnixListener) error {
	ul.SetUnlinkOnClose(true)
	if cm.c == nil {
		if err := cm.open(); err != nil {
			return errors.Join(err, ul.Close())
		}
	}

	var wg sync.WaitGroup
	defer wg.Wait()

	wg.Go(func() {
		for {
			if ctx.Err() != nil {
				break
			}

			conn, err := ul.AcceptUnix()
			if err != nil {
				if !errors.Is(err, os.ErrDeadlineExceeded) {
					log.Println(err)
				}
				continue
			}
			wg.Go(func() {
				if a, _err := cureFromIR(ctx, cm.c, conn); _err != nil {
					log.Println(_err)
				} else {
					log.Printf(
						"fulfilled artifact %s",
						pkg.Encode(cm.c.Ident(a).Value()),
					)
				}
			})
		}
	})

	<-ctx.Done()
	if err := ul.SetDeadline(time.Now()); err != nil {
		return errors.Join(err, ul.Close())
	}
	wg.Wait()
	return ul.Close()
}

// cureRemote cures a [pkg.Artifact] on a daemon.
func cureRemote(
	ctx context.Context,
	addr *net.UnixAddr,
	a pkg.Artifact,
) (*check.Absolute, error) {
	conn, err := net.DialUnix("unix", nil, addr)
	if err != nil {
		return nil, err
	}

	go func() {
		<-ctx.Done()
		_ = conn.SetDeadline(time.Now())
	}()

	if err = pkg.NewIR().EncodeAll(conn, a); err != nil {
		return nil, errors.Join(err, conn.Close())
	} else if err = conn.CloseWrite(); err != nil {
		return nil, errors.Join(err, conn.Close())
	}

	payload, recvErr := io.ReadAll(conn)
	if err = errors.Join(recvErr, conn.Close()); err != nil {
		if errors.Is(err, os.ErrDeadlineExceeded) {
			err = ctx.Err()
		}
		return nil, err
	}

	if len(payload) > 0 && payload[0] == 0 {
		return nil, errors.New(string(payload[1:]))
	}

	var p *check.Absolute
	p, err = check.NewAbs(string(payload))
	return p, err
}