"""Debug sessions (E16): Start → reproduce → Stop, the screenshots, and the evidence under review.

The session itself — what tags a request, its cap, its level — is `app/debugsession.py`. These routes
are the user's handle on their OWN sessions only: another user's id 404s (`owned_or_404`), including
for an admin, who reads everyone's lines in the diagnostics console instead. The shared demo account
cannot record: its log would interleave every visitor under one account.

Screenshots arrive as a raw image body (`image/png`, `image/jpeg`, `image/webp`), not a multipart
form — one image per request, capped while it arrives, and kept only if its bytes really are one of
those types, whatever the Content-Type claimed.
"""

import json
from typing import Any

from fastapi import APIRouter, Depends, HTTPException, Request, Response
from pydantic import BaseModel, Field
from sqlalchemy import select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from app import audit, debugsession, logs, logsink
from app.audit import AuditAction
from app.auth import require_human
from app.db import get_db
from app.issues import bundle, gitea
from app.ratelimit import RateLimiter
from app.refusal import refused
from app.models import DebugScreenshot, DebugSession, User
from app.routes._common import capped_body, issue_refused, not_found, owned_or_404
from app.utils import iso

router = APIRouter(prefix="/api/debug-sessions", tags=["diagnostics"])
log = logs.get_logger(__name__)

# Sessions listed in Settings → Diagnosztika, newest first: enough to reach last week's unsent draft.
LIST_MAX = 20


class StartIn(BaseModel):
    level: debugsession.SessionLevel


_view = debugsession.view

# New sessions a user may open per hour (joining the running one is not counted): a session is a
# place to keep screenshots, and this — with the per-user storage cap — bounds how many there are.
_new_sessions = RateLimiter(max_events=20, window_seconds=3600)


@router.post("")
def start_session(
    body: StartIn,
    user: User = Depends(require_human),
    db: Session = Depends(get_db),
) -> dict:
    """Start recording, or join the recording already running (another tab started it)."""
    joining = debugsession.open_session(db, user) is not None
    if not joining and not _new_sessions.allow(str(user.id)):
        raise refused(429, "debug_session_rate_limited", limit=_new_sessions.max_events)
    try:
        session = debugsession.start(db, user, body.level)
        db.commit()
    except IntegrityError:
        # A concurrent Start won the one-open-per-user index: join that one.
        db.rollback()
        session = debugsession.open_session(db, user)
        if session is None:
            raise refused(409, "debug_session_conflict") from None
    # The rest of THIS request is part of the session too.
    level, until = debugsession.level_for(user, session)
    logs.set_user(user.id, level, until, session.id)
    log.info(
        "debug session started",
        extra=logs.event("debug.session.started", level=session.level, until=iso(session.until)),
    )
    return {"ok": True, "session": _view(db, session)}


@router.post("/{sid}/stop")
def stop_session(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> dict:
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    if session.ended_at is None:
        # Logged BEFORE the session closes, while this request still carries its tag: the last line
        # of the evidence is the Stop itself.
        log.info("debug session stopped", extra=logs.event("debug.session.stopped"))
        debugsession.stop(session)
        db.commit()
        logs.end_session_elevation(session.id)
    return {"ok": True, "session": _view(db, session)}


@router.get("")
def list_sessions(user: User = Depends(require_human), db: Session = Depends(get_db)) -> dict:
    sessions = db.scalars(
        select(DebugSession)
        .where(DebugSession.user_id == user.id)
        .order_by(DebugSession.started_at.desc())
        .limit(LIST_MAX)
    ).all()
    return {"items": [_view(db, s) for s in sessions]}


@router.get("/{sid}")
def get_session(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> dict:
    return _view(db, owned_or_404(db, DebugSession, sid, user, what="debug_session"))


@router.get("/{sid}/events")
def session_events(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> dict:
    """The rows an issue from this session would carry — browser and server, in time order."""
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    rows, total = debugsession.bundle(db, session)
    return {"items": [logsink.serialize(r) for r in rows], "total": total}


# --- the draft and its export ---------------------------------------------------------------
# The composer's own fields (steps, description…) are its business, kept whole so it reopens as it
# was — bounded here so a draft cannot become a place to store anything else.
FORM_MAX_BYTES = 64 * 1024
# Zips a user may build per minute: each holds every screenshot in memory while it is built.
_exports = RateLimiter(max_events=6, window_seconds=60)


class DraftIn(BaseModel):
    title: str = Field(max_length=200)
    # The rendered markdown the export and the issue carry.
    body: str = Field(max_length=50_000)
    # Log rows taken out of the evidence in the review.
    excluded: list[int] = Field(default_factory=list, max_length=debugsession.BUNDLE_MAX)
    form: dict[str, Any] = Field(default_factory=dict)


@router.put("/{sid}/draft")
def save_draft(
    sid: str,
    body: DraftIn,
    user: User = Depends(require_human),
    db: Session = Depends(get_db),
) -> dict:
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    if len(json.dumps(body.form, ensure_ascii=False).encode()) > FORM_MAX_BYTES:
        raise HTTPException(status_code=413, detail={"code": "too_large"})
    # Under the lock: a save that arrives while the issue is being sent waits for the send, and then
    # sees it — the draft of a sent issue cannot change after it.
    debugsession.lock(db, session)
    if session.issue_url is not None:
        # Sent: the issue is on the tracker now, and a draft edited after it would say otherwise.
        raise refused(409, "issue_already_sent")
    debugsession.save_draft(session, body.model_dump())
    db.commit()
    return {"ok": True, "session": _view(db, session)}


@router.get("/{sid}/export")
def export_session(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> Response:
    """The issue as a zip — the text, the two logs and the screenshots — for an instance without an
    issue tracker, or for sending it by hand. Built from the SAVED draft: what the composer shows is
    what it saved."""
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    if not _exports.allow(str(user.id)):
        raise refused(429, "export_rate_limited")
    data = bundle.zipped(bundle.files(db, session))
    name = f"siftlode-debug-{session.started_at:%Y%m%d-%H%M}-{session.id[:6]}.zip"
    return Response(
        content=data,
        media_type="application/zip",
        headers={
            "Content-Disposition": f'attachment; filename="{name}"',
            "Cache-Control": "no-store",
        },
    )


# --- the issue tracker (S4) -----------------------------------------------------------------
# Issues a user may OPEN per hour — finishing a half-sent one, or an attempt refused before the issue
# was opened, is not counted. The composer sends one at a time; this is room for a bad afternoon, not
# a pace anything legitimate keeps up.
_new_issues = RateLimiter(max_events=5, window_seconds=3600)


def _issues_rate_limited() -> HTTPException:
    return refused(429, "issues_rate_limited", limit=_new_issues.max_events)


@router.post("/{sid}/issue")
def send_issue(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> dict:
    """Send the session's issue to the tracker — from the SAVED draft, as the export is built — or
    finish a send that stopped half-way (the issue exists; only what is missing is sent)."""
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    # Held to the end: a second send (another tab, a retry after a timeout) waits for this one and
    # then finds the issue it opened, instead of opening another; an autosave or a screenshot waits
    # too, and then finds the issue sent.
    debugsession.lock(db, session)
    new = session.issue_url is None
    if not new and not debugsession.unfinished(session):
        return {"ok": True, "session": _view(db, session)}
    key = str(user.id)
    if new:
        if not ((session.draft or {}).get("title") or "").strip():
            raise refused(422, "issue_title_required")
        if _new_issues.exhausted(key):
            raise _issues_rate_limited()

    def count_new_issue() -> None:
        if not _new_issues.allow(key):
            raise _issues_rate_limited()

    try:
        gitea.deliver(db, session, before_create=count_new_issue)
    except gitea.GiteaError as exc:
        # Keep what did happen: an issue created before an upload failed stays linked, and the
        # retry does only what is still missing.
        _record_created(db, user, session, new)
        db.commit()
        raise issue_refused(exc) from None
    except HTTPException:
        raise  # the pace, refused before anything was opened
    except Exception:
        # Anything else after the issue was opened must not lose the record that it was: a retry
        # would open a second one.
        _record_created(db, user, session, new)
        db.commit()
        raise
    _record_created(db, user, session, new)
    db.commit()
    return {"ok": True, "session": _view(db, session)}


def _record_created(db: Session, user: User, session: DebugSession, new: bool) -> None:
    if new and session.issue_url:
        audit.record(
            db,
            user.id,
            AuditAction.ISSUE_CREATE,
            target_type="debug_session",
            target_id=session.id,
            summary=session.issue_url,
        )


class PreviewIn(BaseModel):
    text: str = Field(max_length=50_000)


@router.post("/{sid}/preview")
def preview_issue(
    sid: str,
    body: PreviewIn,
    user: User = Depends(require_human),
    db: Session = Depends(get_db),
) -> dict:
    """The body as the tracker will render it. Gitea sanitises its own output; the composer still
    shows it in a sandboxed frame, never in the app's own document."""
    owned_or_404(db, DebugSession, sid, user, what="debug_session")
    try:
        return {"ok": True, "html": gitea.preview(db, body.text)}
    except gitea.GiteaError as exc:
        raise issue_refused(exc) from None


# --- screenshots ---------------------------------------------------------------------------
def _shot_view(shot: DebugScreenshot) -> dict:
    return {"id": shot.id, "mime": shot.mime, "size": shot.size, "created_at": iso(shot.created_at)}


@router.get("/{sid}/screenshots")
def list_screenshots(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> dict:
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    return {"items": [_shot_view(s) for s in debugsession.screenshots(db, session)]}


def _upload_target(
    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> DebugSession:
    return owned_or_404(db, DebugSession, sid, user, what="debug_session")


async def _image_body(request: Request) -> bytes:
    return await capped_body(request, debugsession.SCREENSHOT_MAX_BYTES)


@router.post("/{sid}/screenshots")
def add_screenshot(
    # The owner check FIRST: dependencies resolve in order, so a stranger's upload is refused
    # before a byte of it is read.
    session: DebugSession = Depends(_upload_target),
    data: bytes = Depends(_image_body),
    db: Session = Depends(get_db),
) -> dict:
    try:
        shot = debugsession.add_screenshot(db, session, data)
    except debugsession.ScreenshotRefused as exc:
        raise _screenshot_refused(exc.code) from None
    db.commit()
    return {"ok": True, "screenshot": _shot_view(shot)}


def _screenshot_refused(code: str) -> HTTPException:
    # Literal reasons, one per case: the frontend's contract test reads them to require a sentence
    # for each in both languages.
    if code == "already_sent":
        return refused(409, "screenshot_already_sent")
    if code == "too_many":
        return refused(422, "screenshot_too_many", limit=debugsession.SCREENSHOTS_MAX)
    if code == "storage_full":
        mb = debugsession.SCREENSHOT_USER_MAX_BYTES // (1024 * 1024)
        return refused(422, "screenshot_storage_full", limit=mb)
    if code == "empty":
        return refused(422, "screenshot_empty")
    return refused(422, "screenshot_not_an_image")


def _session_screenshot(db: Session, sid: str, shot_id: int, user: User) -> DebugScreenshot:
    return _screenshot_of(
        db, owned_or_404(db, DebugSession, sid, user, what="debug_session"), shot_id
    )


def _screenshot_of(db: Session, session: DebugSession, shot_id: int) -> DebugScreenshot:
    shot = db.get(DebugScreenshot, shot_id)
    if shot is None or shot.session_id != session.id:
        raise not_found("screenshot")
    return shot


@router.get("/{sid}/screenshots/{shot_id}")
def get_screenshot(
    sid: str, shot_id: int, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> Response:
    shot = _session_screenshot(db, sid, shot_id, user)
    # `nosniff`: the type was checked against the bytes at upload, and the browser must not guess.
    return Response(
        content=shot.data,
        media_type=shot.mime,
        headers={"Cache-Control": "private, max-age=3600", "X-Content-Type-Options": "nosniff"},
    )


@router.delete("/{sid}/screenshots/{shot_id}")
def delete_screenshot(
    sid: str, shot_id: int, user: User = Depends(require_human), db: Session = Depends(get_db)
) -> dict:
    session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
    shot = _screenshot_of(db, session, shot_id)
    try:
        debugsession.remove_screenshot(db, session, shot)
    except debugsession.ScreenshotRefused as exc:
        raise _screenshot_refused(exc.code) from None
    db.commit()
    return {"ok": True, "deleted": shot_id}