"""The Gitea issue tracker a debug session's issue goes to (E16 S4) — measured against Gitea 1.27.1
before a line of this was written (plans/e16-debug-issue.md, S0).

Configured by an admin (sysconfig `issues_gitea_url` / `_repo` / `_token`, the token encrypted at
rest). The repository must be PRIVATE: an issue carries its reporter's log — page titles, filter
values, at Teljes what they typed into search — and a public repository would publish it. That is
checked on every send, not only in the admin's "test connection", because a repository can be made
public after the fact.

What an issue is made of comes from `bundle.files` (the same files the zip export carries). Sending
is three kinds of call, measured:
  * `POST /repos/{repo}/issues` — the title and the body the user wrote;
  * `POST /repos/{repo}/issues/{n}/assets?name=…` — ONE file per request (field `attachment`);
  * `PATCH /repos/{repo}/issues/{n}` — the body again, with the screenshots shown inline once their
    links exist.
A private repository's attachment answers 404 to a browser not signed in to Gitea, which is why the
composer's own preview shows our copies, never these links.

Delivery keeps its progress in the session's draft (`delivery`: the issue number, the files still to
upload, the links of those uploaded, whether the body shows the screenshots yet), so a failure
half-way keeps the issue that exists and a retry does only what is missing — never a second issue.
Every step is checkpointed (the caller's `db.commit`), so what did happen is kept whatever fails
next — and no transaction is held open across these calls. The caller claims the session for the
send first (`debugsession.claim_send`), which is what keeps a second send, an autosave or a
screenshot out of the way. `debugsession.not_uploaded` / `images_pending` read that progress.
"""

from collections.abc import Callable, Iterator
from contextlib import contextmanager
from typing import Any, Literal

import httpx
from sqlalchemy.orm import Session

from app import debugsession, logs, sysconfig
from app.issues import bundle
from app.models import DebugSession

log = logs.get_logger(__name__)

TIMEOUT_SECONDS = 20.0

Reason = Literal[
    "not_configured",  # url, repository or token missing
    "unreachable",  # no answer, or a 5xx
    "bad_token",  # 401/403: the token is wrong or lacks write:issue / read:repository
    "repo_not_found",  # 404 on the repository
    "public_repo",  # the repository is public — an issue would publish the reporter's log
    "issues_disabled",  # the repository has its issue tracker switched off
    "rejected",  # any other 4xx (a file type the instance does not allow, …), or an answer that is
    # not the API's (a redirect — an http:// address behind https —, a page that is not JSON)
]


class GiteaError(Exception):
    def __init__(self, reason: Reason) -> None:
        super().__init__(reason)
        self.reason: Reason = reason


def _settings(db: Session) -> tuple[str, str, str]:
    return (
        sysconfig.get_str(db, "issues_gitea_url").strip().rstrip("/"),
        sysconfig.get_str(db, "issues_gitea_repo").strip().strip("/"),
        sysconfig.get_str(db, "issues_gitea_token").strip(),
    )


def target(db: Session) -> dict | None:
    """Where a report goes, for the composer to say so — the repository — or None when no tracker is
    configured (the report can then only be downloaded)."""
    url, repo, token = _settings(db)
    return {"repo": repo} if url and repo and token else None


@contextmanager
def _client(db: Session) -> Iterator[tuple[httpx.Client, str]]:
    url, repo, token = _settings(db)
    if not (url and repo and token):
        raise GiteaError("not_configured")
    with httpx.Client(
        base_url=f"{url}/api/v1",
        headers={"Authorization": f"token {token}", "Accept": "application/json"},
        timeout=TIMEOUT_SECONDS,
    ) as client:
        yield client, repo


def _call(client: httpx.Client, method: str, path: str, **kwargs) -> httpx.Response:
    try:
        r = client.request(method, path, **kwargs)
    except httpx.HTTPError as exc:
        log.warning(
            "the issue tracker did not answer",
            extra=logs.event("issues.gitea.unreachable", path=path, error=type(exc).__name__),
        )
        raise GiteaError("unreachable") from None
    if r.status_code < 300:
        return r
    # The status only: Gitea's message can quote back what was sent — the user's own title.
    log.warning(
        "the issue tracker refused a call",
        extra=logs.event("issues.gitea.refused", path=path, status=r.status_code),
    )
    if r.status_code in (401, 403):
        raise GiteaError("bad_token")
    if r.status_code == 404:
        raise GiteaError("repo_not_found")
    if r.status_code >= 500:
        raise GiteaError("unreachable")
    raise GiteaError("rejected")


def _json(r: httpx.Response, *keys: str) -> dict[str, Any]:
    """The answer as the API's JSON, holding `keys` — anything else is refused, not a crash, so a
    step after the issue was created cannot take down the request that holds its record.

    The CREATE call is the one place this cannot keep that record: its answer IS the record. An
    answer it cannot read there leaves the session unsent, and a retry opens another issue — the
    price of not being able to tell a refused create from an unreadable one."""
    try:
        data = r.json()
    # silent-ok: not JSON is one of the answers refused (and logged) just below.
    except ValueError:
        data = None
    if not isinstance(data, dict) or any(k not in data for k in keys):
        log.warning(
            "the issue tracker answered something that is not its API",
            extra=logs.event("issues.gitea.unexpected", status=r.status_code),
        )
        raise GiteaError("rejected")
    return data


def _private_repo(client: httpx.Client, repo: str) -> dict:
    data = _json(_call(client, "GET", f"/repos/{repo}"))
    if not data.get("private"):
        raise GiteaError("public_repo")
    if not data.get("has_issues"):
        raise GiteaError("issues_disabled")
    return data


def check(db: Session) -> dict:
    """The admin's "test connection": the repository answers, is private and takes issues."""
    with _client(db) as (client, repo):
        data = _private_repo(client, repo)
    return {"repo": data.get("full_name") or repo, "url": data.get("html_url")}


def preview(db: Session, text: str) -> str:
    """The body as Gitea itself will render it (its markdown flavour, its sanitiser)."""
    with _client(db) as (client, repo):
        r = _call(client, "POST", "/markdown", json={"Text": text, "Mode": "gfm", "Context": repo})
    return r.text


def deliver(
    db: Session,
    session: DebugSession,
    *,
    checkpoint: Callable[[], None],
    before_create: Callable[[], None] | None = None,
) -> str:
    (
        """Send the session's issue, or finish sending it; returns its URL. `checkpoint` persists what
    has happened so far and is called after every step (the caller's commit — this module does not
    decide when a transaction ends). `before_create` runs right before the tracker is asked to open
    a NEW issue — after the checks that can refuse it without asking — and may raise to stop it.""",
    )
    state = debugsession.delivery(session)
    files = bundle.files(db, session)
    attachments = [f for f in files if f.name != "issue.md"]
    with _client(db) as (client, repo):
        _private_repo(client, repo)
        if "number" not in state:
            if before_create is not None:
                before_create()
            created = _json(
                _call(
                    client,
                    "POST",
                    f"/repos/{repo}/issues",
                    json={"title": bundle.title_of(session), "body": bundle.body_of(session)},
                ),
                "number",
                "html_url",
            )
            state = {
                "number": created["number"],
                "pending": [f.name for f in attachments],
                "links": {},
            }
            session.issue_url = created["html_url"]
            debugsession.set_delivery(session, state)
            checkpoint()
            log.info(
                "issue created",
                extra=logs.event("issues.gitea.created", number=created["number"]),
            )
        number = state["number"]
        for item in attachments:
            if item.name not in state["pending"]:
                continue
            asset = _json(
                _call(
                    client,
                    "POST",
                    f"/repos/{repo}/issues/{number}/assets",
                    params={"name": item.name},
                    files={"attachment": (item.name, item.data, item.mime)},
                ),
                "browser_download_url",
            )
            state = {
                **state,
                "pending": [n for n in state["pending"] if n != item.name],
                "links": {**state["links"], item.name: asset["browser_download_url"]},
            }
            debugsession.set_delivery(session, state)
            checkpoint()
        shots = [n for n in state["links"] if n.startswith("screenshot-")]
        if shots and not state.get("images_shown"):
            images = "\n".join(f"![{n}]({state['links'][n]})" for n in sorted(shots))
            body = f"{bundle.body_of(session)}\n\n---\n\n{images}"
            _call(client, "PATCH", f"/repos/{repo}/issues/{number}", json={"body": body})
            debugsession.set_delivery(session, {**state, "images_shown": True})
            checkpoint()
    return session.issue_url or ""