import hashlib

import pytest

from tht.corpus.chunk import ChunkPolicy, chunk
from tht.corpus.models import CanonicalDocument


def document(content: str) -> CanonicalDocument:
    normalized = content.replace("\r\n", "\n").replace("\r", "\n")
    digest = hashlib.sha256(normalized.encode()).hexdigest()
    return CanonicalDocument(
        document_id="doc:abc",
        source_id="source:a",
        source_uri="https://host/a.md",
        source_fingerprint="etag:abc",
        content_hash=f"sha256:{digest}",
        title="A",
        content=normalized,
        media_type="text/markdown",
        pipeline_version="pipe:v1",
        metadata={"owner": "docs"},
    )


def test_chunk_ids_are_stable_for_same_content_and_repeat_runs():
    policy = ChunkPolicy(version="paragraph:v1", max_chars=8)
    first = chunk(document("A\n\nB"), policy)
    second = chunk(document("A\r\n\r\nB"), policy)
    repeated = chunk(document("A\n\nB"), policy)
    assert first == second == repeated


def test_policy_version_changes_ids_without_changing_boundaries():
    doc = document("alpha\n\nbeta")
    first = chunk(doc, ChunkPolicy(version="paragraph:v1", max_chars=6))
    second = chunk(doc, ChunkPolicy(version="paragraph:v2", max_chars=6))
    assert [item.content for item in first] == [item.content for item in second]
    assert [item.chunk_id for item in first] != [item.chunk_id for item in second]


def test_long_non_ascii_tokens_are_hard_split_by_unicode_characters():
    chunks = chunk(document("ééééé世界"), ChunkPolicy(version="chars:v1", max_chars=3))
    assert [item.content for item in chunks] == ["ééé", "éé世", "界"]
    assert all(len(item.content) <= 3 for item in chunks)


def test_chunks_have_contiguous_ordinals_hashes_and_provenance_metadata():
    doc = document("alpha beta gamma")
    chunks = chunk(doc, ChunkPolicy(version="words:v1", max_chars=7))
    assert [item.ordinal for item in chunks] == list(range(len(chunks)))
    assert len({item.chunk_id for item in chunks}) == len(chunks)
    for item in chunks:
        assert item.source_uri == doc.source_uri
        assert item.document_id == doc.document_id
        assert item.pipeline_version == doc.pipeline_version
        assert item.metadata["chunk_policy"] == {"max_chars": 7, "version": "words:v1"}
        assert item.metadata["document"] == {"owner": "docs"}
        assert item.content_hash == "sha256:" + hashlib.sha256(item.content.encode()).hexdigest()


def test_duplicate_chunk_content_cannot_collide_across_ordinals():
    chunks = chunk(document("same\n\nsame"), ChunkPolicy(version="paragraph:v1", max_chars=8))
    assert [item.content for item in chunks] == ["same", "same"]
    assert chunks[0].chunk_id != chunks[1].chunk_id


def test_empty_document_has_no_chunks_and_invalid_policy_is_rejected():
    assert chunk(document(""), ChunkPolicy(version="v1", max_chars=4)) == []
    with pytest.raises(ValueError):
        ChunkPolicy(version="v1", max_chars=0)