"""Unit: the shared ``errorDetailText`` serializer (phase 164, task 02).

Behavior-pins the exported helper under node (the ``_run_node`` house
pattern — the function is pure, so its extracted source runs standalone)
across the full shape matrix, led by the EXACT live FastAPI 422 body of
2026-10-07: a pydantic list-of-objects ``detail`` must serialize to the
``msg`` verbatim — never ``"[object Object]"``, never the rejected
``input`` text (the entries carry the full conversation — it must never
reach the DOM). Source pins: the two chat call sites now read through
the helper, the helper never ``JSON.stringify``-s anything, and the
SEVEN existing guarded detail-readers (tuning.js, theme.js,
document.js, git-sources.js, doc-edit.js, app.js's tuning form and its
image-upload guard) stay byte-identical — no opportunistic refactor.
"""
from __future__ import annotations

import json
import re
import shutil
import subprocess
from pathlib import Path

import pytest

FRONTEND = Path(__file__).resolve().parents[2] / "frontend"
ASSETS = FRONTEND / "assets"
APP_JS = ASSETS / "app.js"
CHAT_PY = Path(__file__).resolve().parents[2] / "app" / "api" / "chat.py"

HAVE_NODE = shutil.which("node") is not None


def _js() -> str:
    return APP_JS.read_text(encoding="utf-8")


def _asset(name: str) -> str:
    return (ASSETS / name).read_text(encoding="utf-8")


def _run_node(script: str) -> str:
    proc = subprocess.run(["node", "-e", script], capture_output=True, text=True, timeout=60)
    assert proc.returncode == 0, f"node failed: {proc.stderr}"
    return proc.stdout


def _fn(js: str, name: str) -> str:
    """The full source of ``export function name(…) {…}`` via
    balanced-brace counting (the test_frontend_* convention — the
    ``export`` prefix still matches the ``function name(`` search)."""
    start = js.find(f"function {name}(")
    assert start != -1, f"{name}() must exist in app.js"
    depth = 0
    for i in range(js.find("{", start), len(js)):
        if js[i] == "{":
            depth += 1
        elif js[i] == "}":
            depth -= 1
            if depth == 0:
                return js[start : i + 1]
    raise AssertionError(f"unbalanced braces in {name}()")


#: Sentinel serialized to the JS literal ``undefined`` (json has none).
class _Undef:
    pass


UNDEFINED = _Undef()


def _lit(v: object) -> str:
    if isinstance(v, _Undef):
        return "undefined"
    return json.dumps(v)


def _serialize(cases: list[tuple[str, object, object]]) -> dict[str, str]:
    """Run the REAL exported ``errorDetailText`` under node over
    ``[(name, value, fallback), …]`` and return ``{name: result}``."""
    script = (
        _fn(_js(), "errorDetailText")
        + "\nconst out = [];\n"
        + "".join(
            f"out.push([{_lit(name)}, errorDetailText({_lit(value)}, {_lit(fallback)})]);\n"
            for name, value, fallback in cases
        )
        + "for (const row of out) console.log(JSON.stringify(row));\n"
    )
    rows = (json.loads(line) for line in _run_node(script).splitlines() if line)
    return {row[0]: row[1] for row in rows}


#: The EXACT live 422 body (phase 164 overview): the follow-up turn of
#: a >32k-char answer, rejected by the old HistoryTurn.text cap. The
#: `input` is the whole rejected conversation — here a marked stand-in
#: that must NEVER appear in the serialized result.
LIVE_422_DETAIL = [
    {
        "type": "string_too_long",
        "loc": ["body", "history", 5, "text"],
        "msg": "String should have at most 600000 characters",
        "input": f"CANARY-INPUT {'x' * 4000}",
    }
]

FB = "FALLBACK-LINE"


# ---------------------------------------------------------------------------
# Behavior — the shape matrix under node (the exported, REAL function)
# ---------------------------------------------------------------------------


@pytest.mark.skipif(not HAVE_NODE, reason="node not available")
def test_live_422_list_detail_serializes_the_msg_only() -> None:
    """The EXACT live 422 body: the entry's ``msg`` verbatim, and the
    result carries NO ``input`` text and no ``"[object Object]"`` —
    the 2026-10-07 failure is unrepresentable (locked A2)."""
    got = _serialize([("live422", LIVE_422_DETAIL, FB)])
    assert got["live422"] == "String should have at most 600000 characters"
    assert "CANARY" not in got["live422"], "the rejected input must never serialize"
    assert "[object Object]" not in got["live422"]


@pytest.mark.skipif(not HAVE_NODE, reason="node not available")
def test_array_entries_join_with_semicolon_space() -> None:
    """Multi-entry arrays join their usable texts with ``"; "``:
    several object ``msg``s, and mixed object + plain-string entries
    (the generalization of the seven guarded copies)."""
    got = _serialize(
        [
            (
                "multi_obj",
                [{"msg": "first problem"}, {"msg": "second problem"}],
                FB,
            ),
            ("mixed", [{"msg": "obj msg"}, "plain string"], FB),
            ("plain_only", ["a", "b"], FB),
            ("number_entry", [42], FB),
        ]
    )
    assert got["multi_obj"] == "first problem; second problem"
    assert got["mixed"] == "obj msg; plain string"
    assert got["plain_only"] == "a; b"
    assert got["number_entry"] == "42"


@pytest.mark.skipif(not HAVE_NODE, reason="node not available")
def test_empty_array_entries_drop_and_all_empty_falls_back() -> None:
    """Entries with neither a usable ``msg`` nor a non-empty string
    drop (objects without msg, empty msgs, nullish, empty strings); an
    all-empty array — and the bare ``[]`` — fall back."""
    got = _serialize(
        [
            ("drop_and_keep", [{"nomsg": 1}, {"msg": ""}, None, "", {"msg": "kept"}], FB),
            ("all_empty", [{"nomsg": 1}, None, ""], FB),
            ("bare_empty", [], FB),
        ]
    )
    assert got["drop_and_keep"] == "kept"
    assert got["all_empty"] == FB
    assert got["bare_empty"] == FB


@pytest.mark.skipif(not HAVE_NODE, reason="node not available")
def test_object_detail_msg_or_fallback() -> None:
    """A plain object with a non-empty ``msg`` serializes it verbatim;
    without one — even carrying a huge rejected ``input`` — it falls
    back (never stringified)."""
    got = _serialize(
        [
            ("obj_msg", {"type": "string_too_long", "msg": "only the msg"}, FB),
            ("obj_nomsg", {"input": "CANARY " * 500}, FB),
            ("obj_empty_msg", {"msg": ""}, FB),
        ]
    )
    assert got["obj_msg"] == "only the msg"
    assert got["obj_nomsg"] == FB
    assert got["obj_empty_msg"] == FB


@pytest.mark.skipif(not HAVE_NODE, reason="node not available")
def test_string_verbatim_incl_server_fixed_copy_otherwise_fallback() -> None:
    """A non-empty string serializes VERBATIM — the pinned server-built
    frame copies ("Question too long…", "The chat model dropped the
    connection…") must reach the user byte-identical. ``""``, null,
    undefined, a number, and a boolean all fall back."""
    server_copy_1 = "Question too long — trim it and re-ask."
    server_copy_2 = "The chat model dropped the connection — try again?"
    # The server-side half of the pin: these ARE the ChatErrorEvent copies.
    chat_py = CHAT_PY.read_text(encoding="utf-8")
    assert f'detail="{server_copy_1}"' in chat_py
    assert f'detail="{server_copy_2}"' in chat_py
    got = _serialize(
        [
            ("server_copy_1", server_copy_1, FB),
            ("server_copy_2", server_copy_2, FB),
            ("plain", "some string", FB),
            ("empty", "", FB),
            ("null", None, FB),
            ("undefined", UNDEFINED, FB),
            ("number", 42, FB),
            ("boolean", True, FB),
        ]
    )
    assert got["server_copy_1"] == server_copy_1
    assert got["server_copy_2"] == server_copy_2
    assert got["plain"] == "some string"
    for name in ("empty", "null", "undefined", "number", "boolean"):
        assert got[name] == FB, name


@pytest.mark.skipif(not HAVE_NODE, reason="node not available")
def test_no_shape_yields_object_object() -> None:
    """TOTALITY sweep: across every shape the helper can meet, no
    result is ever ``"[object Object]"`` (or contains it) — the string
    is unrepresentable at the serializer level."""
    shapes = [
        LIVE_422_DETAIL,
        [{"type": "x", "loc": [1], "msg": "m", "input": "i"}] * 3,
        [{"a": {"b": 1}}],
        {"deep": {"nested": [1, 2]}},
        [[{"msg": "nested"}]],
        "s",
        0,
        None,
        UNDEFINED,
    ]
    got = _serialize([(f"s{i}", v, FB) for i, v in enumerate(shapes)])
    for name, res in got.items():
        assert isinstance(res, str) and res, name
        assert "[object Object]" not in res, name


# ---------------------------------------------------------------------------
# Source pins — the export, the two call sites, the untouched copies
# ---------------------------------------------------------------------------


def test_error_detail_text_is_exported_for_unit_pinning() -> None:
    """The helper is an EXPORTED function (the TURN_TIMEOUT_MS /
    THINKING_NEAR_BOTTOM_PX export-for-unit-pin idiom), declared
    exactly once."""
    js = _js()
    assert re.search(r"^export function errorDetailText\(value, fallback\) \{", js, re.M), (
        "errorDetailText must be an exported top-level function"
    )
    assert js.count("function errorDetailText(") == 1


def test_helper_never_stringifies_never_reads_input_loc_ctx() -> None:
    """LOCKED A2 inside the helper: NO ``JSON.stringify`` anywhere in
    its source, and the words ``input``/``loc``/``ctx`` never appear —
    only ``msg`` and plain strings serialize (the docstring names the
    rule but the FUNCTION body is what this pins)."""
    fn = _fn(_js(), "errorDetailText")
    assert "JSON.stringify" not in fn
    for forbidden in ("input", "loc", "ctx"):
        assert re.search(rf"\b{forbidden}\b", fn) is None, (
            f"the helper must never touch `{forbidden}` (the 422 entries "
            "carry the full rejected conversation)"
        )
    # The docstring above the helper names the live failure + the rule.
    js = _js()
    doc = js[: js.find("function errorDetailText(")][-2500:]
    assert "2026-10-07" in doc and "[object Object]" in doc
    assert "input" in doc, "the docstring names the input-leak rule"


def test_prestream_call_site_reads_through_the_helper() -> None:
    """The pre-stream ``!res.ok || !res.body`` handler: the unguarded
    ``if (body.detail) detail = body.detail`` is GONE, the assignment
    reads ``errorDetailText(body.detail, …)`` with the per-status
    string as the fallback, and the try-around-res.json + non-JSON
    catch keep their shape."""
    js = _js()
    assert "if (body.detail) detail = body.detail;" not in js
    site = js.index('if (!res.ok || !res.body) {')
    block_end = js.index("await readSSE(", site)
    block = js[site:block_end]
    assert "let detail = `Brain's API answered with HTTP ${res.status}.`;" in block
    assert "detail = errorDetailText(body.detail, detail);" in block, (
        "the per-status default is the serializer's fallback"
    )
    assert "} catch { /* non-JSON error body */ }" in block
    # Phase 164 task 03 decorates THIS error (bubbleText + hint) before
    # the throw — the thrown message stays the serialized detail.
    assert "const err = new Error(detail);" in block
    assert "throw err;" in block
    # The fallback is exactly the status line the bubble must show for
    # a non-JSON 500 (phase 164 E2E case b).
    assert "Brain's API answered with HTTP" in block


def test_sse_error_frame_call_site_reads_through_the_helper() -> None:
    """The SSE ``error``-frame throw: ``new Error(errorDetailText(ev.detail,
    "Something went wrong on my side."))`` — and the phase-114
    ``err.hint`` line stays byte-identical right after it."""
    js = _js()
    assert (
        'const err = new Error(errorDetailText(ev.detail, "Something went wrong on my side."));'
        in js
    )
    site = js.index('const err = new Error(errorDetailText(ev.detail,')
    tail = js[site : site + 200]
    assert tail.splitlines()[1].strip() == "err.hint = ev.hint;", (
        "the err.hint channel is untouched"
    )
    assert 'new Error(ev.detail ||' not in js, "the old unguarded read is gone"


#: One guarded 422-reader block per existing site (the seven copies,
#: D2 "stay byte-identical — no opportunistic refactor"): the exact
#: idiom lines, file → (array-msg line, string line).
GUARDED_COPIES: dict[str, tuple[str, str]] = {
    "tuning.js": (
        "      if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {",
        '      if (typeof data.detail === "string" && data.detail) return data.detail;',
    ),
    "theme.js": (
        "      if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {",
        '      if (typeof data.detail === "string" && data.detail) return data.detail;',
    ),
    "document.js": (
        "    if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {",
        '    if (typeof data.detail === "string" && data.detail) return data.detail;',
    ),
    "git-sources.js": (
        "      if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {",
        '      if (typeof data.detail === "string" && data.detail) return data.detail;',
    ),
    "doc-edit.js": (
        "    if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {",
        '    if (typeof data.detail === "string" && data.detail) return data.detail;',
    ),
}


@pytest.mark.parametrize("name", sorted(GUARDED_COPIES))
def test_existing_guarded_readers_are_byte_identical(name: str) -> None:
    """The five external guarded readers keep their EXACT lines
    (indented, verbatim) — the phase touches only the two unguarded
    chat paths."""
    src = _asset(name)
    array_line, string_line = GUARDED_COPIES[name]
    assert array_line in src, f"{name} lost its guarded array-msg line"
    assert string_line in src, f"{name} lost its guarded string line"


def test_app_js_guarded_copies_are_untouched() -> None:
    """app.js's own guarded copies — the tuning-form reader (the
    three-branch idiom) and the image-upload string guard — stay
    byte-identical, and the tuning form was NOT opportunistically
    rewritten onto the new helper (exactly one Array-guard block in
    app.js: the tuning form)."""
    js = _js()
    guard = "if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {"
    assert js.count(guard) == 1
    assert "detail = String(data.detail[0].msg);" in js
    assert "} else if (typeof data.detail === \"string\" && data.detail) {" in js
    assert 'if (typeof body?.detail === "string") detail = body.detail;' in js