package forgekey

import (
	"context"
	"encoding/base64"
	"encoding/binary"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

// Issue 955, area S1: the key the machine's account makes for the forge, and its entry in the keys state.

type fakeState struct{ puts map[string][]byte }

func (f *fakeState) Put(key string, value any) (uint64, error) {
	raw, _ := json.Marshal(value)
	if f.puts == nil {
		f.puts = map[string][]byte{}
	}
	f.puts[key] = raw
	return uint64(len(f.puts)), nil
}

// ed25519Line is a public key line with a well-formed ed25519 blob.
func ed25519Line(seed byte, comment string) string {
	blob := []byte{}
	for _, part := range [][]byte{[]byte("ssh-ed25519"), make([]byte, 32)} {
		part2 := append([]byte(nil), part...)
		if len(part2) == 32 {
			part2[0] = seed
		}
		l := make([]byte, 4)
		binary.BigEndian.PutUint32(l, uint32(len(part2)))
		blob = append(append(blob, l...), part2...)
	}
	return "ssh-ed25519 " + base64.StdEncoding.EncodeToString(blob) + " " + comment
}

// keygenRunner stands in for ssh-keygen -t ed25519: it writes the pair the command names.
func keygenRunner(calls *[][]string) Runner {
	return func(ctx context.Context, env []string, name string, args ...string) Ran {
		*calls = append(*calls, append([]string{name}, args...))
		var file, comment string
		for i, a := range args {
			switch a {
			case "-f":
				file = args[i+1]
			case "-C":
				comment = args[i+1]
			}
		}
		if name != "ssh-keygen" || file == "" {
			return Ran{Status: 1, Stderr: "unexpected"}
		}
		os.WriteFile(file, []byte("-----BEGIN OPENSSH PRIVATE KEY-----\nPRIVATE-SECRET\n"), 0o600)
		os.WriteFile(file+".pub", []byte(ed25519Line(7, comment)+"\n"), 0o644)
		return Ran{}
	}
}

func newKeeper(t *testing.T, home string, st *fakeState, calls *[][]string) *KeyKeeper {
	return &KeyKeeper{Home: home, Node: "g14", Account: "nox", Kind: KindMachine, Run: keygenRunner(calls), State: st,
		Now: func() time.Time { return time.Date(2026, 10, 16, 12, 0, 0, 0, time.UTC) }}
}

func TestKeeperMakesTheKeyAndWritesItsEntry(t *testing.T) {
	home := t.TempDir()
	st, calls := &fakeState{}, &[][]string{}
	if err := newKeeper(t, home, st, calls).Once(context.Background()); err != nil {
		t.Fatal(err)
	}
	raw, ok := st.puts["g14.nox"]
	if !ok || len(st.puts) != 1 {
		t.Fatalf("entries = %v, want one under g14.nox", st.puts)
	}
	var e map[string]string
	json.Unmarshal(raw, &e)
	if e["node"] != "g14" || e["account"] != "nox" || e["kind"] != "machine" || e["at"] != "2026-10-16T12:00:00Z" {
		t.Errorf("entry = %v", e)
	}
	if !strings.HasPrefix(e["public"], "ssh-ed25519 ") || !strings.HasSuffix(e["public"], " nox@g14 (mesh)") {
		t.Errorf("public = %q", e["public"])
	}
	if !strings.HasPrefix(e["fingerprint"], "SHA256:") {
		t.Errorf("fingerprint = %q", e["fingerprint"])
	}
	if strings.Contains(strings.ToUpper(string(raw)), "PRIVATE") {
		t.Errorf("the entry carries private material: %s", raw)
	}
	cmd := strings.Join((*calls)[0], " ")
	for _, want := range []string{"-t ed25519", "-N ", "-C nox@g14 (mesh)", filepath.Join(home, ".ssh", "mesh_ed25519")} {
		if !strings.Contains(cmd, want) {
			t.Errorf("ssh-keygen call %q lacks %q", cmd, want)
		}
	}
}

func TestKeeperKeepsAnExistingKeyByteForByte(t *testing.T) {
	home := t.TempDir()
	os.MkdirAll(filepath.Join(home, ".ssh"), 0o700)
	priv, pub := filepath.Join(home, ".ssh", "mesh_ed25519"), filepath.Join(home, ".ssh", "mesh_ed25519.pub")
	os.WriteFile(priv, []byte("mine"), 0o600)
	os.WriteFile(pub, []byte(ed25519Line(9, "nox@g14 (mesh)")+"\n"), 0o644)
	st, calls := &fakeState{}, &[][]string{}
	k := newKeeper(t, home, st, calls)
	if err := k.Once(context.Background()); err != nil {
		t.Fatal(err)
	}
	if len(*calls) != 0 {
		t.Errorf("ssh-keygen ran over an existing key: %v", *calls)
	}
	if b, _ := os.ReadFile(priv); string(b) != "mine" {
		t.Errorf("private file changed: %q", b)
	}
	if _, ok := st.puts["g14.nox"]; !ok {
		t.Errorf("no entry for the existing key")
	}
	// A second round with nothing changed writes nothing.
	delete(st.puts, "g14.nox")
	k.Once(context.Background())
	if len(st.puts) != 0 {
		t.Errorf("an unchanged key was put again")
	}
}

func TestKeeperNeverTouchesTheOperatorsOwnKeys(t *testing.T) {
	home := t.TempDir()
	os.MkdirAll(filepath.Join(home, ".ssh"), 0o700)
	own := filepath.Join(home, ".ssh", "id_ed25519")
	os.WriteFile(own, []byte("operator"), 0o600)
	st, calls := &fakeState{}, &[][]string{}
	newKeeper(t, home, st, calls).Once(context.Background())
	if b, _ := os.ReadFile(own); string(b) != "operator" {
		t.Errorf("the operator's key changed")
	}
}

// 1469/AC1: an empty home, kind builder, account mesh-build-go: ssh-keygen once, for the one file, and the entry
// carries the kind, the public half and its fingerprint.
func TestBuilderKeyIsMadeOnceAndPutWithItsKind(t *testing.T) {
	home := t.TempDir()
	st, calls := &fakeState{}, &[][]string{}
	k := newKeeper(t, home, st, calls)
	k.Account, k.Kind = "mesh-build-go", KindBuilder
	if err := k.Once(context.Background()); err != nil {
		t.Fatal(err)
	}
	if len(*calls) != 1 || !strings.Contains(strings.Join((*calls)[0], " "), filepath.Join(home, ".ssh", "mesh_ed25519")) {
		t.Errorf("ssh-keygen calls = %v, want one for mesh_ed25519 in the home", *calls)
	}
	var e KeyEntry
	if err := json.Unmarshal(st.puts["g14.mesh-build-go"], &e); err != nil {
		t.Fatalf("entry under g14.mesh-build-go: %v (%v)", err, st.puts)
	}
	pub, _ := os.ReadFile(filepath.Join(home, ".ssh", "mesh_ed25519.pub"))
	pk, _ := ParseKeyLine(string(pub))
	if e.Kind != "builder" || e.Public != strings.TrimSpace(string(pub)) || e.Fingerprint != pk.Fingerprint || e.Fingerprint == "" {
		t.Errorf("entry = %+v", e)
	}
}

// 1469/AC2: an existing key, Once twice: ssh-keygen never, one put.
func TestExistingKeyIsPutOnceAcrossTwoRounds(t *testing.T) {
	home := t.TempDir()
	os.MkdirAll(filepath.Join(home, ".ssh"), 0o700)
	os.WriteFile(filepath.Join(home, ".ssh", "mesh_ed25519"), []byte("mine"), 0o600)
	os.WriteFile(filepath.Join(home, ".ssh", "mesh_ed25519.pub"), []byte(ed25519Line(9, "x")+"\n"), 0o644)
	st, calls := &countState{}, &[][]string{}
	k := newKeeper(t, home, &fakeState{}, calls)
	k.State = st
	for i := 0; i < 2; i++ {
		if err := k.Once(context.Background()); err != nil {
			t.Fatal(err)
		}
	}
	if len(*calls) != 0 || st.n != 1 {
		t.Errorf("ssh-keygen calls = %d, puts = %d, want 0 and 1", len(*calls), st.n)
	}
}

type countState struct{ n int }

func (c *countState) Put(string, any) (uint64, error) { c.n++; return uint64(c.n), nil }

// 1469/AC3: the entry's JSON is ssh-client's own (mesh-catalog modules/ssh-client keykeeper_test.go's keys
// entry: node, account, kind, public, fingerprint, at, in that order); mesh-catalog's gitea provider reads it.
func TestKeyEntryJSONIsSSHClients(t *testing.T) {
	raw, err := json.Marshal(KeyEntry{Node: "g14", Account: "nox", Kind: "machine", Public: "ssh-ed25519 AAAA nox@g14 (mesh)",
		Fingerprint: "SHA256:abc", At: "2026-10-16T12:00:00Z"})
	if err != nil {
		t.Fatal(err)
	}
	want := `{"node":"g14","account":"nox","kind":"machine","public":"ssh-ed25519 AAAA nox@g14 (mesh)","fingerprint":"SHA256:abc","at":"2026-10-16T12:00:00Z"}`
	if string(raw) != want {
		t.Errorf("entry JSON = %s\nwant %s", raw, want)
	}
}

type failState struct{}

func (failState) Put(string, any) (uint64, error) { return 0, errors.New("no grant yet") }

// 1469/AC4: a failing put is said, and the next look is after KeyRetry, not KeyRound.
func TestKeepSaysAFailedPutAndRetriesSoon(t *testing.T) {
	home := t.TempDir()
	k := newKeeper(t, home, &fakeState{}, &[][]string{})
	k.State = failState{}
	ctx, cancel := context.WithCancel(context.Background())
	var said []string
	var pauses []time.Duration
	k.After = func(d time.Duration) <-chan time.Time {
		pauses = append(pauses, d)
		cancel()
		return make(chan time.Time)
	}
	k.Keep(ctx, func(f string, a ...any) { said = append(said, fmt.Sprintf(f, a...)) })
	if len(said) != 1 || !strings.Contains(said[0], "no grant yet") {
		t.Errorf("said = %v", said)
	}
	if len(pauses) != 1 || pauses[0] != KeyRetry {
		t.Errorf("pauses = %v, want [%v]", pauses, KeyRetry)
	}
}