"""Round-trip tests for tokenize_period / detokenize_to_period in src/tokenizer.py.

Fixture files used (all from tests/fixtures/):
  valid_c_major.chord     — already canonical; 8 bars, chorus, has F/A slash chord
  valid_fsharp_major.chord — F# major → C major (shift=6); 4 bars
  valid_b_minor.chord     — B minor → A minor (shift=10); 4 bars
  valid_gsharp_minor.chord — G# minor → A minor (shift=1); 4 bars
"""

from pathlib import Path

import pytest

from src.chord_parser import ChordTokens, parse_chord_symbol
from src.tokenizer import (
    ID_TO_TOKEN,
    TOKEN_TO_ID,
    VOCAB,
    ChordPeriod,
    detokenize_to_period,
    parse_chord_file,
    tokenize_period,
    transpose_to_canonical,
)

FIXTURES = Path(__file__).parent / "fixtures"

VALID_FIXTURES = [
    "valid_c_major.chord",
    "valid_fsharp_major.chord",
    "valid_b_minor.chord",
    "valid_gsharp_minor.chord",
]


# ---------------------------------------------------------------------------
# Vocabulary
# ---------------------------------------------------------------------------


class TestVocabulary:
    def test_vocab_has_85_tokens(self):
        assert len(VOCAB) == 85

    def test_no_duplicate_tokens(self):
        assert len(set(VOCAB)) == 85

    def test_token_to_id_covers_all_vocab(self):
        assert len(TOKEN_TO_ID) == 85

    def test_id_to_token_covers_all_vocab(self):
        assert len(ID_TO_TOKEN) == 85

    def test_ids_are_contiguous_from_zero(self):
        for i, tok in enumerate(VOCAB):
            assert TOKEN_TO_ID[tok] == i

    def test_id_to_token_is_inverse_of_token_to_id(self):
        for i, tok in enumerate(VOCAB):
            assert ID_TO_TOKEN[i] == tok

    def test_special_tokens_at_front(self):
        assert VOCAB[:4] == ["<BOS>", "<EOS>", "<PAD>", "<UNK>"]

    def test_structural_tokens_at_end(self):
        assert VOCAB[-3:] == ["HOLD", "NC", "BAR"]

    def test_all_roots_present(self):
        for note in ("C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"):
            assert f"ROOT_{note}" in TOKEN_TO_ID

    def test_all_qualities_present(self):
        for qual_tok in (
            "QUAL_maj", "QUAL_m", "QUAL_dim", "QUAL_aug",
            "QUAL_sus2", "QUAL_sus4", "QUAL_maj7", "QUAL_m7",
            "QUAL_7", "QUAL_m7b5", "QUAL_dim7", "QUAL_mM7",
            "QUAL_7sus4", "QUAL_aug7", "QUAL_6", "QUAL_m6",
            "QUAL_add9", "QUAL_m_add9",
        ):
            assert qual_tok in TOKEN_TO_ID

    def test_all_extensions_present(self):
        for ext in ("none", "9", "b9", "#9", "11", "#11", "13", "b13"):
            assert f"EXT_{ext}" in TOKEN_TO_ID

    def test_all_bass_notes_present(self):
        assert "BASS_root" in TOKEN_TO_ID
        for note in ("C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"):
            assert f"BASS_{note}" in TOKEN_TO_ID


# ---------------------------------------------------------------------------
# Tokenize structure
# ---------------------------------------------------------------------------


class TestTokenizeStructure:
    def test_starts_with_bos(self):
        p = parse_chord_file(FIXTURES / "valid_c_major.chord")
        assert tokenize_period(p)[0] == TOKEN_TO_ID["<BOS>"]

    def test_ends_with_eos(self):
        p = parse_chord_file(FIXTURES / "valid_c_major.chord")
        assert tokenize_period(p)[-1] == TOKEN_TO_ID["<EOS>"]

    def test_metadata_order_after_bos(self):
        p = parse_chord_file(FIXTURES / "valid_c_major.chord")
        toks = [ID_TO_TOKEN[i] for i in tokenize_period(p)]
        assert toks[1] == "MODE_major"
        assert toks[2] == "TIME_4/4"
        assert toks[3] == "SUB_4"
        assert toks[4] == "STYLE_other"  # 'unspecified' is not in VOCAB → falls back to STYLE_other
        assert toks[5] == "FUNC_chorus"

    def test_bar_token_count_matches_bar_count(self):
        p = parse_chord_file(FIXTURES / "valid_c_major.chord")
        ids = tokenize_period(p)
        assert sum(1 for i in ids if i == TOKEN_TO_ID["BAR"]) == len(p.bars)

    def test_minor_period_emits_mode_minor(self):
        p = parse_chord_file(FIXTURES / "valid_b_minor.chord")
        toks = [ID_TO_TOKEN[i] for i in tokenize_period(p)]
        assert toks[1] == "MODE_minor"

    def test_missing_function_emits_func_unspecified(self):
        p = parse_chord_file(FIXTURES / "valid_b_minor.chord")
        toks = [ID_TO_TOKEN[i] for i in tokenize_period(p)]
        assert toks[5] == "FUNC_unspecified"

    def test_all_ids_in_vocab_range(self):
        for fixture_name in VALID_FIXTURES:
            p = parse_chord_file(FIXTURES / fixture_name)
            assert all(0 <= i < 85 for i in tokenize_period(p))

    def test_non_canonical_key_transposed_before_encoding(self):
        # F# major: first chord F#maj7 → Cmaj7 after shift=6; ROOT_C is at index 6.
        p = parse_chord_file(FIXTURES / "valid_fsharp_major.chord")
        ids = tokenize_period(p)
        assert ID_TO_TOKEN[ids[6]] == "ROOT_C"


# ---------------------------------------------------------------------------
# Round-trip
# ---------------------------------------------------------------------------


class TestRoundTrip:
    @pytest.mark.parametrize("fixture_name", VALID_FIXTURES)
    def test_chord_symbols_survive_round_trip(self, fixture_name):
        p = parse_chord_file(FIXTURES / fixture_name)
        canonical = transpose_to_canonical(p)
        recovered = detokenize_to_period(tokenize_period(p))

        assert len(recovered.bars) == len(canonical.bars)
        for bar_c, bar_r in zip(canonical.bars, recovered.bars):
            assert len(bar_c) == len(bar_r)
            for sym_c, sym_r in zip(bar_c, bar_r):
                if sym_c in (".", "NC", "?"):
                    assert sym_r == sym_c
                else:
                    assert parse_chord_symbol(sym_r) == parse_chord_symbol(sym_c)

    @pytest.mark.parametrize("fixture_name", VALID_FIXTURES)
    def test_metadata_survives_round_trip(self, fixture_name):
        p = parse_chord_file(FIXTURES / fixture_name)
        canonical = transpose_to_canonical(p)
        recovered = detokenize_to_period(tokenize_period(p))

        assert recovered.key == canonical.key
        assert recovered.time == canonical.time
        assert recovered.subdivision == canonical.subdivision
        assert recovered.style == canonical.style
        assert recovered.function == canonical.function

    @pytest.mark.parametrize("fixture_name", VALID_FIXTURES)
    def test_bar_count_survives_round_trip(self, fixture_name):
        p = parse_chord_file(FIXTURES / fixture_name)
        recovered = detokenize_to_period(tokenize_period(p))
        assert len(recovered.bars) == len(p.bars)

    def test_c_major_chord_identity(self):
        # C major is already canonical — chord tokens must reproduce exactly.
        p = parse_chord_file(FIXTURES / "valid_c_major.chord")
        recovered = detokenize_to_period(tokenize_period(p))
        assert recovered.key == "C_major"
        for bar_p, bar_r in zip(p.bars, recovered.bars):
            for sym_p, sym_r in zip(bar_p, bar_r):
                if sym_p not in (".", "NC", "?"):
                    assert parse_chord_symbol(sym_r) == parse_chord_symbol(sym_p)

    def test_slash_chord_root_and_bass_survive(self):
        # F/A in C major: root=F maj, bass=A must survive the round-trip.
        p = parse_chord_file(FIXTURES / "valid_c_major.chord")
        recovered = detokenize_to_period(tokenize_period(p))
        t = parse_chord_symbol(recovered.bars[2][0])
        assert t == ChordTokens("F", "maj", "none", "A")

    def test_fsharp_major_tonic_becomes_c_after_round_trip(self):
        p = parse_chord_file(FIXTURES / "valid_fsharp_major.chord")
        recovered = detokenize_to_period(tokenize_period(p))
        t = parse_chord_symbol(recovered.bars[0][0])
        assert t.root == "C"
        assert t.quality == "maj7"

    def test_b_minor_tonic_becomes_am_after_round_trip(self):
        p = parse_chord_file(FIXTURES / "valid_b_minor.chord")
        recovered = detokenize_to_period(tokenize_period(p))
        t = parse_chord_symbol(recovered.bars[0][0])
        assert t.root == "A"
        assert t.quality == "m"