# Copyright (c) 2026 Krzysztof Rudnicki. MIT licence.
"""Image fetching and JSON path walking."""

from __future__ import annotations

import base64
from collections.abc import Callable

import httpx
import pytest

from signal_bot.http_client import ImageFetcher, ImageFetchError

IMAGE = b"\x89PNG\r\n\x1a\nfake"

# The callable httpx.MockTransport expects -- not a bot command handler.
MockHandler = Callable[[httpx.Request], httpx.Response]


def _fetcher(handler: MockHandler) -> ImageFetcher:
    return ImageFetcher(httpx.AsyncClient(transport=httpx.MockTransport(handler)))


def _api(payload: object, image: bytes = IMAGE) -> MockHandler:
    def handler(request: httpx.Request) -> httpx.Response:
        if "images" in str(request.url) or "breeds" in str(request.url):
            return httpx.Response(200, json=payload)
        return httpx.Response(200, content=image)

    return handler


async def test_fetches_via_list_then_key_path() -> None:
    fetcher = _fetcher(_api([{"url": "https://cdn.example/cat.png"}]))
    encoded = await fetcher.fetch_base64("https://api/images/search", [0, "url"])
    assert base64.b64decode(encoded) == IMAGE


async def test_fetches_via_single_key_path() -> None:
    fetcher = _fetcher(_api({"message": "https://cdn.example/dog.png"}))
    encoded = await fetcher.fetch_base64("https://api/breeds/x", ["message"])
    assert base64.b64decode(encoded) == IMAGE


async def test_negative_index_is_supported() -> None:
    fetcher = _fetcher(_api([{"url": "https://cdn.example/cat.png"}]))
    encoded = await fetcher.fetch_base64("https://api/images/search", [-1, "url"])
    assert base64.b64decode(encoded) == IMAGE


@pytest.mark.parametrize(
    ("payload", "path"),
    [
        ({"other": "x"}, ["message"]),
        ([], [0, "url"]),
        ([{"url": "x"}], [5, "url"]),
        ({"message": "x"}, [0]),
        ([{"url": "x"}], ["message"]),
    ],
)
async def test_missing_element_raises(payload: object, path: list) -> None:
    fetcher = _fetcher(_api(payload))
    with pytest.raises(ImageFetchError, match="no element at"):
        await fetcher.fetch_base64("https://api/images/search", path)


@pytest.mark.parametrize("payload", [{"message": 42}, {"message": ""}])
async def test_non_url_element_raises(payload: object) -> None:
    fetcher = _fetcher(_api(payload))
    with pytest.raises(ImageFetchError, match="is not a URL"):
        await fetcher.fetch_base64("https://api/breeds/x", ["message"])


async def test_api_error_propagates() -> None:
    fetcher = _fetcher(lambda r: httpx.Response(503))
    with pytest.raises(httpx.HTTPStatusError):
        await fetcher.fetch_base64("https://api/images/search", [0, "url"])


async def test_image_download_error_propagates() -> None:
    def handler(request: httpx.Request) -> httpx.Response:
        if "images" in str(request.url):
            return httpx.Response(200, json=[{"url": "https://cdn.example/cat.png"}])
        return httpx.Response(404)

    with pytest.raises(httpx.HTTPStatusError):
        await _fetcher(handler).fetch_base64("https://api/images/search", [0, "url"])


async def test_rewrite_swaps_the_thumbnail_for_the_full_size_photo() -> None:
    """The URL actually downloaded is the rewritten one, not the one in the JSON."""
    seen: list[str] = []

    def handler(request: httpx.Request) -> httpx.Response:
        seen.append(str(request.url))
        if "observations" in str(request.url):
            return httpx.Response(200, json={"url": "https://cdn/1/square.jpeg"})
        return httpx.Response(200, content=IMAGE)

    encoded = await _fetcher(handler).fetch_base64(
        "https://api/observations", ["url"], ("/square.", "/large.")
    )
    assert base64.b64decode(encoded) == IMAGE
    assert seen[-1] == "https://cdn/1/large.jpeg"


async def test_rewrite_that_matches_nothing_leaves_the_url_alone() -> None:
    seen: list[str] = []

    def handler(request: httpx.Request) -> httpx.Response:
        seen.append(str(request.url))
        if "observations" in str(request.url):
            return httpx.Response(200, json={"url": "https://cdn/1/original.jpeg"})
        return httpx.Response(200, content=IMAGE)

    await _fetcher(handler).fetch_base64(
        "https://api/observations", ["url"], ("/square.", "/large.")
    )
    assert seen[-1] == "https://cdn/1/original.jpeg"