package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"os"

	"hg.lukegb.com/lukegb/depot/go/nix/nixdrv"
	"hg.lukegb.com/lukegb/depot/go/nix/nixstore"
)

func ensure(ctx context.Context, d *nixstore.Daemon, at *nixstore.ActivityTracker, path string) error {
	return d.EnsurePath(at, path)
}

var rs nixdrv.LocalFSResolver

func loadDerivation(ctx context.Context, path string) (*nixdrv.Derivation, error) {
	return rs.LoadDerivation(path)
}

func buildDerivation(ctx context.Context, d *nixstore.Daemon, at *nixstore.ActivityTracker, path string) error {
	drv, err := loadDerivation(ctx, path)
	if err != nil {
		return fmt.Errorf("loading derivation: %w", err)
	}

	basicDrv, err := drv.ToBasicDerivation(rs)
	if err != nil {
		return fmt.Errorf("resolving: %w", err)
	}

	brs, err := d.BuildDerivation(at, path, basicDrv, nixstore.BMNormal)
	if err != nil {
		return err
	}
	log.Printf("build result: %v", brs)
	return nil
}

func main() {
	flag.Parse()

	badCall := func(f string, xs ...interface{}) {
		fmt.Fprintf(os.Stderr, f+"\n", xs...)
		flag.Usage()
		os.Exit(1)
	}

	if flag.NArg() < 1 {
		badCall("need a subcommand")
	}

	var cmd func(context.Context, *nixstore.Daemon, *nixstore.ActivityTracker) error
	switch flag.Arg(0) {
	case "ensure":
		if flag.NArg() != 2 {
			badCall("`ensure` needs a store path")
		}
		cmd = func(ctx context.Context, d *nixstore.Daemon, at *nixstore.ActivityTracker) error {
			return ensure(ctx, d, at, flag.Arg(1))
		}
	case "show-derivation":
		if flag.NArg() != 2 {
			badCall("`show-derivation` needs a derivation")
		}
		cmd = func(ctx context.Context, d *nixstore.Daemon, at *nixstore.ActivityTracker) error {
			drv, err := loadDerivation(ctx, flag.Arg(1))
			if err != nil {
				return err
			}
			fmt.Printf("%#v\n", drv)
			return nil
		}
	case "build-derivation":
		if flag.NArg() != 2 {
			badCall("`build-derivation` needs a derivation")
		}
		cmd = func(ctx context.Context, d *nixstore.Daemon, at *nixstore.ActivityTracker) error {
			return buildDerivation(ctx, d, at, flag.Arg(1))
		}
	default:
		badCall("bad subcommand %s", flag.Arg(0))
	}

	at := nixstore.NewActivityTracker()

	d, err := nixstore.OpenDaemon(nixstore.DaemonSock)
	if err != nil {
		log.Fatalf("OpenDaemon: %v", err)
	}
	defer d.Close()

	ctx := context.Background()
	if err := cmd(ctx, d, at); err != nil {
		log.Fatalf("%s: %s", flag.Arg(0), err)
	}
}