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

package main

import (
	"cmp"
	"context"
	"encoding/json"
	"fmt"
	"os"
	"sync"

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

	source "git.mothstuff.lol/lukeshu/eclipse"
	"git.mothstuff.lol/lukeshu/eclipse/lib/leader"
)

func min[T cmp.Ordered](a, b T) T {
	if a < b {
		return a
	}
	return b
}

func keys[K comparable, V any](m map[K]V) []K {
	ret := make([]K, 0, len(m))
	for k := range m {
		ret = append(ret, k)
	}
	return ret
}

type Set[T comparable] map[T]struct{}

func (s Set[T]) Has(v T) bool {
	_, ok := s[v]
	return ok
}

func parallel[T any](
	nWorkers int,
	generator func(yield func(T)),
	consumer func(T),
) {
	ch := make(chan T)
	go func() {
		defer close(ch)
		generator(func(v T) { ch <- v })
	}()

	var wg sync.WaitGroup
	wg.Add(nWorkers)
	for i := 0; i < nWorkers; i++ {
		go func() {
			defer wg.Done()
			for v := range ch {
				consumer(v)
			}
		}()
	}
	wg.Wait()
}

func Trigger(cfgFile string, allowedRepos Set[string]) (err error) {
	maybeSetErr := func(_err error) {
		if err == nil && _err != nil {
			err = _err
		}
	}

	cfg, err := leader.LoadConfig(cfgFile)
	if err != nil {
		return err
	}

	actions, err := cfg.Actions()
	if err != nil {
		return err
	}

	store, err := cfg.DB()
	if err != nil {
		return err
	}
	defer func() { maybeSetErr(store.Close()) }()

	repos := map[string]map[string]string{}
	for _, action := range actions {
		for _, trigger := range action.Triggers {
			if len(allowedRepos) > 0 && !allowedRepos.Has(trigger.RepoURL) {
				continue
			}
			if repos[trigger.RepoURL] == nil {
				repos[trigger.RepoURL] = make(map[string]string, 1)
			}
			repos[trigger.RepoURL][trigger.Rev] = ""
		}
	}

	cache := cfg.GitCache()

	// Fetch.
	parallel[string](min(cfg.ParallelDownloads, len(repos)),
		func(yield func(string)) {
			for repo := range repos {
				yield(repo)
			}
		},
		func(repo string) {
			if err := cache.Fetch(os.Stderr, repo); err != nil {
				fmt.Fprintf(os.Stderr, "error: updating %q: %v\n", repo, err)
			}
		},
	)

	// Resolve revs.
	parallel[string](len(repos),
		func(yield func(string)) {
			for repo := range repos {
				yield(repo)
			}
		},
		func(repo string) {
			exprs := keys(repos[repo])
			hashs, err := cache.RevParse(os.Stderr, repo, exprs...)
			if err != nil {
				fmt.Fprintf(os.Stderr, "error: resolving in %q: %v\n", repo, err)
				return
			}
			for i := range hashs {
				repos[repo][exprs[i]] = hashs[i]
			}
		},
	)

	// Trigger.
	updatedTriggers := make(map[string]string)
	for _, action := range actions {
		var triggerExprs []string
		var triggerVals []string
		for _, trigger := range action.Triggers {
			newVal, ok := repos[trigger.RepoURL][trigger.Rev]
			if !ok {
				continue
			}
			triggerExprBytes, err := json.Marshal(trigger)
			if err != nil {
				return err
			}
			triggerExpr := string(triggerExprBytes)
			oldVal, _ := store.GetTrigger(triggerExpr)
			if newVal != oldVal {
				triggerExprs = append(triggerExprs, triggerExpr)
				triggerVals = append(triggerVals, newVal)
				updatedTriggers[triggerExpr] = newVal
			}
		}
		if len(triggerExprs) > 0 {
			jobID, err := store.NewJob(triggerExprs, triggerVals, action.Run)
			if err != nil {
				return err
			}
			fmt.Printf("created job %v:\n", jobID)
			for i := range triggerExprs {
				fmt.Printf("\ttrigger: %s => %q\n", triggerExprs[i], triggerVals[i])
			}
			fmt.Printf("\trun: %q\n", action.Run)
		}
	}
	for expr, val := range updatedTriggers {
		fmt.Printf("remembering that %s => %q\n", expr, val)
		if err := store.SetTrigger(expr, val); err != nil {
			return err
		}
	}

	return nil
}

func main() {
	argparser := &cobra.Command{
		Use:   os.Args[0] + " [flags] [ALLOWED_REPOS...]",
		Short: "Add new jobs to the leader",

		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.DefaultLeaderConfigFile,
		"Config file to use")
	_ = argparser.MarkFlagFilename("config", "yml", "yaml")
	argparser.RunE = func(_ *cobra.Command, args []string) error {
		allowedRepos := make(Set[string], len(args))
		for _, repo := range args {
			allowedRepos[repo] = struct{}{}
		}
		return Trigger(cfgFile, allowedRepos)
	}

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