"""Tests for src/generate.py — prefix encoding and position tracking."""

import pytest

from src.generate import _encode_prefix, _HOLD, _NC, _ROOT_START, _BASS_START, _BASS_END
from src.tokenizer import TOKEN_TO_ID


def test_encode_prefix_chord_only():
    # "Cmaj7" in C major (shift=0) → ROOT_C QUAL_maj7 EXT_none BASS_root
    ids, n_pos = _encode_prefix(["Cmaj7"], shift=0)
    assert len(ids) == 4
    assert n_pos == 1
    assert ids[0] == TOKEN_TO_ID["ROOT_C"]
    assert ids[3] == TOKEN_TO_ID["BASS_root"]


def test_encode_prefix_hold():
    ids, n_pos = _encode_prefix(["."], shift=0)
    assert ids == [_HOLD]
    assert n_pos == 1


def test_encode_prefix_nc():
    ids, n_pos = _encode_prefix(["NC"], shift=0)
    assert ids == [_NC]
    assert n_pos == 1


def test_encode_prefix_mixed():
    # "Abmaj7 . Fm7 . Db . Bbm ." — what the user tried and got a parse error on
    symbols = ["Abmaj7", ".", "Fm7", ".", "Db", ".", "Bbm", "."]
    # Ab major → shift to canonical C major = (0 - 8) % 12 = 4
    shift = (0 - 8) % 12
    ids, n_pos = _encode_prefix(symbols, shift=shift)
    assert n_pos == 8                     # 8 bar positions
    # Dots become single HOLD tokens; chords become 4-token groups
    # Total tokens: 4 chords × 4 + 4 holds × 1 = 20
    assert len(ids) == 20
    # Every dot position must be a HOLD
    hold_positions = [1, 3, 5, 7]        # indices in the symbol list
    # Reconstruct expected token positions: chord at 0→tokens 0-3, dot→token 4, etc.
    token_idx = 0
    for sym in symbols:
        if sym == ".":
            assert ids[token_idx] == _HOLD
            token_idx += 1
        else:
            assert _ROOT_START <= ids[token_idx] <= TOKEN_TO_ID["ROOT_B"]
            assert _BASS_START <= ids[token_idx + 3] <= _BASS_END
            token_idx += 4


def test_encode_prefix_position_count_with_holds():
    # Mixed prefix: 2 chords and 2 holds = 4 positions
    ids, n_pos = _encode_prefix(["Am", ".", "G", "."], shift=0)
    assert n_pos == 4
    assert len(ids) == 2 * 4 + 2 * 1   # 10 tokens