package capsule

import (
	"bytes"
	"errors"
	"testing"

	"filippo.io/age"

	datekeys "g.activething.com/go/DateKeys"
)

// decryptAll reads the plaintext into one buffer of the ciphertext's size, so
// that no outgrown buffer keeps a copy of I_PAYLOAD, and still reports a
// truncated STREAM, which the age reader signals with io.ErrUnexpectedEOF.
func TestDecryptAll(t *testing.T) {
	id, err := age.GenerateX25519Identity()
	if err != nil {
		t.Fatal(err)
	}
	const chunk = 64 << 10
	for _, size := range []int{0, 1, 511, 512, 513, chunk, chunk + 1, 2*chunk + 100} {
		plaintext := bytes.Repeat([]byte{0xab}, size)
		ct, err := encryptAll(plaintext, id.Recipient())
		if err != nil {
			t.Fatal(err)
		}
		out, err := decryptAll(ct, id)
		if err != nil || !bytes.Equal(out, plaintext) {
			t.Fatalf("%d bytes: %v", size, err)
		}
		if cap(out) != len(ct) {
			t.Errorf("%d bytes: a buffer of %d bytes for a ciphertext of %d", size, cap(out), len(ct))
		}
		if size == 0 {
			continue
		}
		// The last chunk removed: a truncation at a chunk boundary.
		last := size % chunk
		if last == 0 {
			last = chunk
		}
		for _, cut := range []int{len(ct) - 1, len(ct) - (last + 16)} {
			if _, err := decryptAll(ct[:cut], id); !errors.Is(err, datekeys.ErrIntegrity) {
				t.Errorf("%d bytes cut to %d of %d: %v", size, cut, len(ct), err)
			}
		}
	}
}