// Copyright (C) 2023-2024  Umorpha Systems
// SPDX-License-Identifier: AGPL-3.0-or-later

package main

import (
	"context"
	"crypto/rand"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math/big"
	"net/http"
	"net/url"
	"os"
	"time"

	"github.com/datawire/ocibuild/pkg/cliutil"
	"github.com/spf13/cobra"

	source "git.mothstuff.lol/lukeshu/eclipse"
	"git.mothstuff.lol/lukeshu/eclipse/lib/common"
	"git.mothstuff.lol/lukeshu/eclipse/lib/follower"
)

func main() {
	argparser := &cobra.Command{
		Use:   os.Args[0] + " [flags] JOBS_URL",
		Short: "Choose a job from the leader server",
		Args:  cliutil.WrapPositionalArgs(cobra.NoArgs),

		SilenceErrors: true, // we'll handle this ourselves after .ExecuteContext()
		SilenceUsage:  true, // FlagErrorFunc will handle this

		CompletionOptions: cobra.CompletionOptions{
			DisableDefaultCmd: true,
		},
	}
	argparser.SetFlagErrorFunc(cliutil.FlagErrorFunc)
	argparser.SetHelpTemplate(cliutil.HelpTemplate)

	var cfgFile string
	argparser.Flags().StringVar(&cfgFile, "config", source.DefaultFollowerConfigFile,
		"Config file to use")
	_ = argparser.MarkFlagFilename("config", "yml", "yaml")

	argparser.RunE = func(*cobra.Command, []string) error {
		return Pick(cfgFile)
	}

	ctx := context.Background()
	if err := argparser.ExecuteContext(ctx); err != nil {
		fmt.Fprintf(os.Stderr, "%v: error: %v\n", argparser.CommandPath(), err)
		os.Exit(1)
	}
}

func randInt(max int) (int, error) {
	bigN, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
	if err != nil {
		return 0, err
	}
	return int(bigN.Int64()), nil
}

func Pick(cfgFile string) error {
	cfg, err := follower.LoadConfig(cfgFile)
	if err != nil {
		return err
	}

	u, err := url.Parse(cfg.LeaderURL)
	if err != nil {
		return err
	}
	u.Path = "/jobs/"
	u.RawQuery = url.Values{
		"status": []string{"new"},
		"wait":   []string{"true"},
	}.Encode()

	httpClient := &http.Client{
		Timeout: 45 * time.Second,
	}

	// TODO: If we go 1 minute without an "HTTP 100 Continue"
	// keepalive, then fail with a timeout.
	resp, err := httpClient.Get(u.String())
	if err != nil {
		return err
	}
	if resp.StatusCode != http.StatusOK {
		err := fmt.Errorf("HTTP %s", resp.Status)
		body, _ := io.ReadAll(resp.Body)
		if len(body) > 0 {
			err = fmt.Errorf("%w\n%s", err, body)
		}
		return err
	}

	bodyBytes, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}
	var options []common.Job
	if err := json.Unmarshal(bodyBytes, &options); err != nil {
		return err
	}

	if len(options) == 0 {
		return errors.New("no jobs to choose from; this indicates a server bug, it should never return an empty non-error response")
	}

	n, err := randInt(len(options))
	if err != nil {
		return err
	}

	u.Path = fmt.Sprintf("/jobs/%d/", options[n].ID)
	u.RawQuery = ""

	fmt.Println(u)

	return nil
}