"""Tests for parse_chord_file() and transpose_to_canonical() in src/tokenizer.py.

Fixture files live in tests/fixtures/:
  valid_c_major.chord       — already canonical (C major, 8 bars, has a // comment)
  valid_fsharp_major.chord  — F# major with a slash chord (F#/A#)
  valid_b_minor.chord       — B minor
  valid_gsharp_minor.chord  — G# minor with a slash chord (Bmaj7/F#)
  invalid_bar_count.chord   — bar 1 has 5 positions instead of 4
  invalid_chord_symbol.chord — bar 2 contains the invalid symbol 'Xyz'
"""

from pathlib import Path

import pytest

from src.chord_parser import ChordTokens, parse_chord_symbol
from src.tokenizer import ChordFormatError, ChordPeriod, parse_chord_file, transpose_to_canonical

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


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------


def fixture(name: str) -> Path:
    return FIXTURES / name


# ---------------------------------------------------------------------------
# parse_chord_file — valid files
# ---------------------------------------------------------------------------


class TestParseChordFile:
    def test_c_major_header_fields(self):
        p = parse_chord_file(fixture("valid_c_major.chord"))
        assert p.title == "C major test"
        assert p.key == "C_major"
        assert p.time == "4/4"
        assert p.subdivision == 4
        assert p.style == "other"
        assert p.function == "chorus"

    def test_c_major_bar_count(self):
        p = parse_chord_file(fixture("valid_c_major.chord"))
        assert len(p.bars) == 8

    def test_c_major_bar_positions(self):
        p = parse_chord_file(fixture("valid_c_major.chord"))
        assert p.bars[0] == ["C", ".", ".", "."]
        assert p.bars[2] == ["F/A", ".", ".", "."]  # slash chord preserved verbatim
        assert p.bars[7] == ["G7", ".", ".", "."]

    def test_c_major_comments_stripped(self):
        # The first bar line ends with '// first half'; no '//' should bleed into positions.
        p = parse_chord_file(fixture("valid_c_major.chord"))
        for bar in p.bars:
            assert not any("//" in pos for pos in bar)

    def test_each_bar_has_expected_position_count(self):
        p = parse_chord_file(fixture("valid_c_major.chord"))
        for bar in p.bars:
            assert len(bar) == 4  # 4/4, subdivision=4

    def test_fsharp_major_parses(self):
        p = parse_chord_file(fixture("valid_fsharp_major.chord"))
        assert p.key == "F#_major"
        assert len(p.bars) == 4
        assert p.bars[0][0] == "F#maj7"
        assert p.bars[2][2] == "F#/A#"  # slash chord preserved verbatim

    def test_b_minor_parses(self):
        p = parse_chord_file(fixture("valid_b_minor.chord"))
        assert p.key == "B_minor"
        assert p.function == "unspecified"  # no function header field
        assert p.bars[0][0] == "Bm"
        assert p.bars[1][0] == "C#m7b5"

    def test_gsharp_minor_parses(self):
        p = parse_chord_file(fixture("valid_gsharp_minor.chord"))
        assert p.key == "G#_minor"
        assert len(p.bars) == 4
        assert p.bars[2][0] == "Bmaj7/F#"  # slash chord

    def test_hold_positions_preserved(self):
        p = parse_chord_file(fixture("valid_c_major.chord"))
        # Every position after the first in each bar is '.'
        for bar in p.bars:
            assert bar[1] == "."
            assert bar[2] == "."
            assert bar[3] == "."


# ---------------------------------------------------------------------------
# parse_chord_file — error cases
# ---------------------------------------------------------------------------


class TestParseChordFileErrors:
    def test_invalid_bar_count_raises(self):
        with pytest.raises(ChordFormatError):
            parse_chord_file(fixture("invalid_bar_count.chord"))

    def test_invalid_bar_count_error_mentions_bar_number(self):
        with pytest.raises(ChordFormatError) as exc_info:
            parse_chord_file(fixture("invalid_bar_count.chord"))
        assert "bar 1" in str(exc_info.value)

    def test_invalid_bar_count_error_mentions_filename(self):
        with pytest.raises(ChordFormatError) as exc_info:
            parse_chord_file(fixture("invalid_bar_count.chord"))
        assert "invalid_bar_count.chord" in str(exc_info.value)

    def test_invalid_chord_symbol_raises(self):
        with pytest.raises(ChordFormatError):
            parse_chord_file(fixture("invalid_chord_symbol.chord"))

    def test_invalid_chord_symbol_error_mentions_bar_number(self):
        with pytest.raises(ChordFormatError) as exc_info:
            parse_chord_file(fixture("invalid_chord_symbol.chord"))
        assert "bar 2" in str(exc_info.value)

    def test_invalid_chord_symbol_error_mentions_filename(self):
        with pytest.raises(ChordFormatError) as exc_info:
            parse_chord_file(fixture("invalid_chord_symbol.chord"))
        assert "invalid_chord_symbol.chord" in str(exc_info.value)


# ---------------------------------------------------------------------------
# transpose_to_canonical — F# major → C major  (shift = 6)
# ---------------------------------------------------------------------------


class TestTransposeFsharpMajor:
    def setup_method(self):
        self._period = parse_chord_file(fixture("valid_fsharp_major.chord"))
        self._t = transpose_to_canonical(self._period)

    def test_key_updated_to_c_major(self):
        assert self._t.key == "C_major"

    def test_tonic_chord_becomes_c(self):
        # F#maj7 (bar 0) → Cmaj7
        assert self._t.bars[0][0] == "Cmaj7"

    def test_second_degree_chord(self):
        # D#m7 (bar 1) → Am7  (D#=3, 3+6=9=A)
        assert self._t.bars[1][0] == "Am7"

    def test_fourth_degree_chord(self):
        # Bmaj7 (bar 2 pos 0) → Fmaj7  (B=11, 11+6=17→5=F)
        assert self._t.bars[2][0] == "Fmaj7"

    def test_fifth_degree_chord(self):
        # C# (bar 3) → G  (C#=1, 1+6=7=G)
        tokens = parse_chord_symbol(self._t.bars[3][0])
        assert tokens.root == "G"
        assert tokens.quality == "maj"

    def test_slash_chord_root_transposed(self):
        # F#/A# (bar 2, pos 2): root F# → C
        tokens = parse_chord_symbol(self._t.bars[2][2])
        assert tokens.root == "C"

    def test_slash_chord_bass_transposed(self):
        # F#/A# (bar 2, pos 2): bass A#(=10) → E (10+6=16→4=E)
        tokens = parse_chord_symbol(self._t.bars[2][2])
        assert tokens.bass == "E"

    def test_slash_chord_full_tokens(self):
        tokens = parse_chord_symbol(self._t.bars[2][2])
        assert tokens == ChordTokens("C", "maj", "none", "E")

    def test_hold_positions_unchanged(self):
        # Bars 0, 1, 3 are single-chord bars: positions 1–3 must remain '.'.
        # Bar 2 has a chord at position 2 (F#/A# → Cmaj/E) — tested separately.
        for bar_idx in (0, 1, 3):
            assert all(pos == "." for pos in self._t.bars[bar_idx][1:])

    def test_bar_count_preserved(self):
        assert len(self._t.bars) == len(self._period.bars)


# ---------------------------------------------------------------------------
# transpose_to_canonical — G# minor → A minor  (shift = 1)
# ---------------------------------------------------------------------------


class TestTransposeGsharpMinor:
    def setup_method(self):
        self._period = parse_chord_file(fixture("valid_gsharp_minor.chord"))
        self._t = transpose_to_canonical(self._period)

    def test_key_updated_to_a_minor(self):
        assert self._t.key == "A_minor"

    def test_tonic_becomes_a(self):
        # G#m (bar 0) → Am  (G#=8, 8+1=9=A)
        assert self._t.bars[0][0] == "Am"

    def test_second_degree_chord(self):
        # A#maj7 (bar 1) → Bmaj7  (A#=10, 10+1=11=B)
        assert self._t.bars[1][0] == "Bmaj7"

    def test_slash_chord_root_transposed(self):
        # Bmaj7/F# (bar 2): root B(=11) → C (11+1=0=C)
        tokens = parse_chord_symbol(self._t.bars[2][0])
        assert tokens.root == "C"

    def test_slash_chord_bass_transposed(self):
        # Bmaj7/F# (bar 2): bass F#(=6) → G (6+1=7=G)
        tokens = parse_chord_symbol(self._t.bars[2][0])
        assert tokens.bass == "G"

    def test_slash_chord_full_tokens(self):
        tokens = parse_chord_symbol(self._t.bars[2][0])
        assert tokens == ChordTokens("C", "maj7", "none", "G")

    def test_fourth_bar(self):
        # D#7 (bar 3) → E7  (D#=3, 3+1=4=E)
        assert self._t.bars[3][0] == "E7"


# ---------------------------------------------------------------------------
# transpose_to_canonical — already canonical (C major)
# ---------------------------------------------------------------------------


class TestTransposeCMajorIdentity:
    def test_returns_same_object(self):
        # Fast path: shift == 0, original period returned unchanged.
        p = parse_chord_file(fixture("valid_c_major.chord"))
        t = transpose_to_canonical(p)
        assert t is p

    def test_key_unchanged(self):
        p = parse_chord_file(fixture("valid_c_major.chord"))
        assert transpose_to_canonical(p).key == "C_major"


# ---------------------------------------------------------------------------
# transpose_to_canonical — B minor → A minor  (shift = 10)
# ---------------------------------------------------------------------------


class TestTransposeBMinor:
    def setup_method(self):
        self._period = parse_chord_file(fixture("valid_b_minor.chord"))
        self._t = transpose_to_canonical(self._period)

    def test_key_updated_to_a_minor(self):
        assert self._t.key == "A_minor"

    def test_tonic_becomes_a(self):
        # Bm (B=11): 11+10=21→9=A
        assert self._t.bars[0][0] == "Am"

    def test_half_diminished_chord(self):
        # C#m7b5 (C#=1): 1+10=11=B → Bm7b5
        assert self._t.bars[1][0] == "Bm7b5"

    def test_major_chord_transposed(self):
        # D (D=2): 2+10=12→0=C → Cmaj
        tokens = parse_chord_symbol(self._t.bars[2][0])
        assert tokens.root == "C"
        assert tokens.quality == "maj"

    def test_dominant_seventh_transposed(self):
        # F#7 (F#=6): 6+10=16→4=E → E7
        assert self._t.bars[3][0] == "E7"