"""Tests for CRX Refined (cluster-then-infer)."""

import pytest
from bex.crx_refined import crx_refined, crx_with_confidence, _cluster_by_structure
from bex.crx import CRX


class TestClusterByStructure:
    def test_empty(self):
        assert _cluster_by_structure([]) == {}

    def test_single_sequence(self):
        result = _cluster_by_structure([['a', 'b', 'c']])
        assert len(result) == 1
        assert ('a', 'c', 'short') in result

    def test_same_start_end_same_length(self):
        seqs = [['a', 'b', 'c'], ['a', 'd', 'c']]
        result = _cluster_by_structure(seqs)
        # Both start with 'a', end with 'c', length 3 (short)
        assert len(result) == 1

    def test_different_start_end(self):
        seqs = [['a', 'b', 'c'], ['x', 'y', 'z']]
        result = _cluster_by_structure(seqs)
        assert len(result) == 2

    def test_length_buckets(self):
        seqs = [
            ['a', 'b', 'a'],           # short
            ['a', 'b', 'c', 'a'],       # short (different last)
            ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'a'],  # med (8, same first/last)
            ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'a'],  # long (9, same first/last)
        ]
        result = _cluster_by_structure(seqs)
        keys = set(result.keys())
        # 'a'→'a' short, 'a'→'a' med, 'a'→'a' long = 3 clusters for same first/last
        # 'a'→'a' short has 1 seq, med has 1, long has 1
        assert ('a', 'a', 'short') in keys
        assert ('a', 'a', 'med') in keys
        assert ('a', 'a', 'long') in keys


class TestCrxRefined:
    def test_empty(self):
        assert crx_refined([]) == 'ε'

    def test_single_sequence(self):
        result = crx_refined([['a', 'b', 'c']])
        assert result is not None
        assert 'a' in result

    def test_identical_sequences(self):
        seqs = [['a', 'b', 'c']] * 5
        result = crx_refined(seqs)
        assert 'a' in result
        assert 'b' in result

    def test_linear_pattern(self):
        seqs = [['a', 'b', 'c'], ['a', 'b', 'c'], ['a', 'b', 'c']]
        result = crx_refined(seqs)
        # All same → should be tight
        assert result == CRX().infer(seqs)

    def test_branching_pattern(self):
        # Paper counterexample
        seqs = [['a', 'b', 'c'], ['a', 'd', 'e'], ['a', 'b', 'e']]
        result = crx_refined(seqs)
        refined_g = crx_refined(seqs)
        # Refined should produce SOMETHING (not crash)
        assert refined_g is not None
        assert 'a' in refined_g

    def test_falls_back_to_standard(self):
        # Very diverse sequences — no cluster large enough
        seqs = [['a'], ['b'], ['c'], ['d']]
        result = crx_refined(seqs, min_cluster=2)
        # Should fall back to standard CRX
        assert result == CRX().infer(seqs)


class TestCrxWithConfidence:
    def test_empty(self):
        result = crx_with_confidence([])
        assert result['grammar'] == 'ε'
        assert result['confidence'] == 1.0
        assert result['n_clusters'] == 0

    def test_returns_all_fields(self):
        seqs = [['a', 'b', 'c'], ['a', 'b', 'c']]
        result = crx_with_confidence(seqs)
        assert 'grammar' in result
        assert 'confidence' in result
        assert 'n_clusters' in result
        assert 'largest_cluster' in result
        assert 'n_sequences' in result

    def test_confidence_range(self):
        seqs = [['a', 'b', 'c'], ['a', 'd', 'e']]
        result = crx_with_confidence(seqs)
        assert 0.0 <= result['confidence'] <= 1.0

    def test_confident_when_tight(self):
        seqs = [['a', 'b', 'c']] * 10
        result = crx_with_confidence(seqs)
        assert result['confidence'] >= 0.9

    def test_less_confident_when_diverse(self):
        # Many sequences sharing first/last but with different internals
        seqs = [
            ['a', 'b', 'c', 'z'],
            ['a', 'x', 'y', 'z'],
            ['a', 'p', 'q', 'z'],
            ['a', 'r', 's', 'z'],
        ]
        result = crx_with_confidence(seqs)
        # All share first/last → one cluster, but internals differ
        # Confidence depends on how many pairs the cluster grammar captures
        assert result['n_clusters'] >= 1


class TestComparisonWithStandard:
    """Compare refined vs standard CRX on various inputs."""

    def test_linear_same_result(self):
        seqs = [['a', 'b', 'c']] * 5
        assert crx_refined(seqs) == CRX().infer(seqs)

    def test_single_symbol(self):
        seqs = [['a']] * 5
        assert crx_refined(seqs) == 'a'

    def test_two_symbols(self):
        seqs = [['a', 'b']] * 5
        assert crx_refined(seqs) == 'a.b'

    def test_disjunction(self):
        seqs = [['a', 'b'], ['a', 'c']]
        result = crx_refined(seqs)
        # Should have a disjunction somewhere
        assert '+' in result