package rootparticipation

import (
	"context"
	"encoding/json"
	"os"
	"path/filepath"
	"sync"
	"testing"
)

type testDisk struct {
	dir string
	mu  sync.Mutex
}

func (d *testDisk) Read(n string) ([]byte, error) { return os.ReadFile(filepath.Join(d.dir, n)) }
func (d *testDisk) Write(n string, b []byte) error {
	return os.WriteFile(filepath.Join(d.dir, n), b, 0600)
}
func (d *testDisk) Remove(n string) error { return os.Remove(filepath.Join(d.dir, n)) }
func (d *testDisk) Names() ([]string, error) {
	es, e := os.ReadDir(d.dir)
	var out []string
	for _, v := range es {
		out = append(out, v.Name())
	}
	return out, e
}
func (d *testDisk) Close() error { return nil }
func (d *testDisk) Lock(context.Context, string) (func(), error) {
	d.mu.Lock()
	return d.mu.Unlock, nil
}
func censusFixture(t *testing.T) Ledger {
	t.Helper()
	s := &testDisk{dir: t.TempDir()}
	b, _ := json.Marshal(Census{Schema: 1, Box: "box", Enrollment: "en", Migration: 1, Revision: 1, Complete: true, LaunchRevision: 1})
	if err := s.Write("census.json", b); err != nil {
		t.Fatal(err)
	}
	return Ledger{State: s, Box: "box", Enrollment: "en", VerifyLaunches: func(context.Context, uint64) error { return nil }}
}

func TestPlan14ExecutionUpdateExclusion(t *testing.T) {
	for _, first := range []string{"acquisition", "update"} {
		t.Run(first, func(t *testing.T) {
			l := censusFixture(t)
			entered, release := make(chan struct{}), make(chan struct{})
			acquire := func() error {
				return l.Acquire(t.Context(), func() error {
					close(entered)
					<-release
					return l.State.Write("shop.example.json", []byte(`{"Schema":1,"Status":"pending"}`))
				})
			}
			update := func() error { return l.BeginUpdate(t.Context(), "update-1") }
			var winner, loser func() error
			if first == "acquisition" {
				winner, loser = acquire, update
			} else {
				l.VerifyLaunches = func(context.Context, uint64) error { close(entered); <-release; return nil }
				winner, loser = update, acquire
			}
			done := make(chan error, 1)
			go func() { done <- winner() }()
			<-entered
			other := make(chan error, 1)
			go func() { other <- loser() }()
			// Removing every service mirror cannot change the root transaction.
			data := t.TempDir()
			if err := os.Mkdir(filepath.Join(data, ".hostexec"), 0700); err != nil {
				t.Fatal(err)
			}
			if err := os.RemoveAll(filepath.Join(data, ".hostexec")); err != nil {
				t.Fatal(err)
			}
			close(release)
			if err := <-done; err != nil {
				t.Fatal(err)
			}
			if err := <-other; err == nil {
				t.Fatal("update and acquisition both succeeded")
			}
		})
	}
}
func TestPlan14ParticipationRequiresCompleteRootCensus(t *testing.T) {
	l := censusFixture(t)
	if err := l.Idle(t.Context()); err != nil {
		t.Fatal(err)
	}
	if err := l.State.Remove("census.json"); err != nil {
		t.Fatal(err)
	}
	if err := l.Idle(t.Context()); err == nil {
		t.Fatal("missing root census became empty")
	}
	if err := l.Acquire(t.Context(), func() error { t.Fatal("unknown history acquired"); return nil }); err == nil {
		t.Fatal("unknown history admitted")
	}
}