from __future__ import annotations

from datetime import datetime, timezone
from urllib.parse import urlencode

from quart import Blueprint, abort, current_app, redirect, render_template, request, session, url_for
from sqlalchemy import select

from steward.audit.service import mark_day_groups
from steward.auth.middleware import require_role, safe_next_url
from steward.core import formatting as fmt
from steward.core.audit import audit_request
from steward.core.paging import keyset, next_page
from steward.models.hosts import Host
from steward.models.timeline import TimelineEntry
from steward.models.users import UserRole
from steward.timeline import catalog, changes, config as tl_config, service as tl

timeline_bp = Blueprint("timeline", __name__)


def _filters() -> dict:
    a = request.args
    return {"host": a.get("host", "").strip(), "area": a.get("area", "").strip(),
            "kind": a.get("kind", "").strip(), "hidden": a.get("hidden") == "1"}


@timeline_bp.get("/timeline/")
@require_role(UserRole.viewer)
async def timeline():
    """Everything that happened, newest first, a page at a time as the reader
    scrolls; ?before=<cursor> is the next page's rows alone (core.paging)."""
    f = _filters()
    async with current_app.db_sessionmaker() as db:
        cfg = await tl_config.load(db)
        stmt = tl.query(cfg, host=f["host"], area=f["area"], kind=f["kind"],
                        include_hidden=f["hidden"])
        stmt = keyset(stmt, TimelineEntry.at, TimelineEntry.id, request.args.get("before"))
        rows, after = next_page((await db.execute(stmt)).scalars().all(), lambda e: (e.at, e.id))
        items = _editable(await tl.views(db, cfg, rows))
        hosts = [] if request.args.get("before") else \
            list((await db.execute(select(Host.name).order_by(Host.name))).scalars())
    last_group = mark_day_groups(items, fmt.zone(session.get("tz")), request.args.get("group", ""),
                                 at=lambda item: item["entry"].at)
    keep = {k: v for k, v in (("host", f["host"]), ("area", f["area"]), ("kind", f["kind"]),
                              ("hidden", "1" if f["hidden"] else "")) if v}
    back = "/timeline/" + ("?" + urlencode(keep) if keep else "")
    ctx = {"items": items, "after": after, "last_group": last_group, "filters": f, "keep": keep, "back": back,
           "areas": cfg.areas, "kinds": catalog.KINDS,
           "hosts": hosts if not f["host"] or f["host"] in hosts else [f["host"], *hosts]}
    if request.args.get("before"):
        return await render_template("timeline/_rows.html", **ctx)
    return await render_template("timeline/list.html", **ctx)


@timeline_bp.get("/timeline/host/<host_id>")
@require_role(UserRole.viewer)
async def host_card(host_id: str):
    """A host's newest entries, for its page (loaded into it)."""
    async with current_app.db_sessionmaker() as db:
        host = await db.get(Host, host_id)
        if host is None:
            return "", 404
        cfg = await tl_config.load(db)
        items = _editable(await tl.recent_for_host(db, cfg, host.name))
    return await render_template("timeline/_host_card.html", host=host, items=items)


def _editable(items: list[dict]) -> list[dict]:
    """Mark the entries this reader may edit: changes they recorded, or any as an admin."""
    for item in items:
        item["editable"] = changes.can_edit(item["entry"], session.get("user_id"), session.get("user_role"))
    return items


# ── Changes recorded by hand ────────────────────────────────────────────────

def _local(value: str | None) -> datetime | None:
    """A datetime-local field, in the reader's own zone."""
    value = (value or "").strip()
    if not value:
        return None
    try:
        local = datetime.fromisoformat(value)
    except ValueError:
        raise ValueError(f"{value!r} is not a date and time.") from None
    return local.replace(tzinfo=fmt.zone(session.get("tz"))).astimezone(timezone.utc)


def _as_local(when: datetime) -> str:
    return when.astimezone(fmt.zone(session.get("tz"))).strftime("%Y-%m-%dT%H:%M")


async def _change_page(db, cfg, *, values: dict, entry=None, back: str, error: str | None = None,
                       status: int = 200):
    from steward.models.hosts import Host
    hosts = list((await db.execute(select(Host.name).order_by(Host.name))).scalars())
    # A host named by an entry and since removed stays ticked, so a save keeps it.
    hosts += [h for h in values["hosts"] if h not in hosts]
    return await render_template("timeline/change_form.html", values=values, entry=entry, back=back,
                                 error=error, hosts=hosts, areas=cfg.areas), status


def _back(raw: str | None) -> str:
    """Where saving returns: the page the form was opened from, else the timeline."""
    return safe_next_url(raw) or "/timeline/"


async def _checked(db, cfg) -> tuple[dict | None, dict, str, str | None]:
    """(fields, values, back, error) from the posted form: the fields
    changes.fields checked, or None and why not, with the form's own values
    to show again."""
    form = await request.form
    values = {"summary": form.get("summary", ""), "area": form.get("area", ""),
              "hosts": form.getlist("hosts"), "subject": form.get("subject", ""),
              "note": form.get("note", ""), "at": form.get("at", "")}
    back = _back(form.get("back"))
    try:
        f = await changes.fields(db, cfg, summary=values["summary"], area=values["area"],
                                 hosts=values["hosts"], subject=values["subject"],
                                 note=values["note"], at=_local(values["at"]))
    except ValueError as exc:
        return None, values, back, str(exc)
    return f, values, back, None


@timeline_bp.get("/timeline/changes/new")
@require_role(UserRole.operator)
async def new_change():
    """The form for recording a change; ?host= ticks a host, ?back= is where saving returns."""
    host = request.args.get("host", "").strip()
    values = {"summary": "", "area": "", "hosts": [host] if host else [], "subject": "", "note": "",
              "at": _as_local(datetime.now(timezone.utc))}
    async with current_app.db_sessionmaker() as db:
        cfg = await tl_config.load(db)
        return await _change_page(db, cfg, values=values, back=_back(request.args.get("back")))


@timeline_bp.post("/timeline/changes")
@require_role(UserRole.operator)
async def record_change():
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            cfg = await tl_config.load(db)
            f, values, back, error = await _checked(db, cfg)
            if error:
                return await _change_page(db, cfg, values=values, back=back, error=error, status=400)
            entry = changes.log(db, f, author_id=session.get("user_id"), actor=session.get("username", ""))
    await audit_request("timeline.change_recorded", entity_type="timeline_entry", entity_id=entry.id,
                        detail={"name": entry.summary, "hosts": entry.hosts, "area": entry.area})
    return redirect(back)


async def _own(db, entry_id: str):
    """The recorded change `entry_id`, when this reader may edit it; else 404 or 403."""
    entry = await changes.get(db, entry_id)
    if entry is None:
        abort(404)
    if not changes.can_edit(entry, session.get("user_id"), session.get("user_role")):
        abort(403)
    return entry


@timeline_bp.get("/timeline/changes/<entry_id>/edit")
@require_role(UserRole.operator)
async def edit_change(entry_id: str):
    async with current_app.db_sessionmaker() as db:
        entry = await _own(db, entry_id)
        cfg = await tl_config.load(db)
        values = {"summary": entry.summary, "area": entry.area, "hosts": list(entry.hosts),
                  "subject": entry.subject or "", "note": (entry.detail or {}).get("note") or "",
                  "at": _as_local(entry.at)}
        return await _change_page(db, cfg, values=values, entry=entry,
                                  back=_back(request.args.get("back")))


@timeline_bp.post("/timeline/changes/<entry_id>")
@require_role(UserRole.operator)
async def save_change(entry_id: str):
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            entry = await _own(db, entry_id)
            cfg = await tl_config.load(db)
            f, values, back, error = await _checked(db, cfg)
            if error:
                return await _change_page(db, cfg, values=values, entry=entry, back=back,
                                          error=error, status=400)
            changes.edit(entry, f)
    await audit_request("timeline.change_edited", entity_type="timeline_entry", entity_id=entry_id,
                        detail={"name": f["summary"]})
    return redirect(back)


@timeline_bp.post("/timeline/changes/<entry_id>/delete")
@require_role(UserRole.operator)
async def delete_change(entry_id: str):
    form = await request.form
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            entry = await _own(db, entry_id)
            summary = entry.summary
            await db.delete(entry)
    await audit_request("timeline.change_deleted", entity_type="timeline_entry", entity_id=entry_id,
                        detail={"name": summary})
    return redirect(_back(form.get("back")))


@timeline_bp.get("/settings/timeline/")
@require_role(UserRole.admin)
async def settings_page():
    async with current_app.db_sessionmaker() as db:
        cfg = await tl_config.load(db)
        from steward.core.settings import get_setting
        retention = int(await get_setting(db, "timeline.retention_days") or 0)
    return await render_template("settings/timeline.html", **_settings_ctx(cfg, retention))


def _settings_ctx(cfg, retention: int, error: str | None = None) -> dict:
    by_kind = {k: [t for t in catalog.TYPES.values() if t.kind == k] for k in catalog.KINDS}
    return {"cfg": cfg, "retention": retention, "error": error, "kinds": catalog.KINDS,
            "by_kind": {k: v for k, v in by_kind.items() if v}}


@timeline_bp.post("/settings/timeline/")
@require_role(UserRole.admin)
async def save_settings():
    from steward.core.settings import set_setting
    form = await request.form
    try:
        retention = max(0, int(form.get("retention_days") or 0))
    except ValueError:
        retention = None
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            cfg = await tl_config.load(db)
            new, error = tl_config.edited(cfg, form)
            if error is None and retention is None:
                error = "Keep for: a whole number of days, or 0 to keep everything."
            if error is not None:
                kept = retention if retention is not None else 0
                return await render_template("settings/timeline.html",
                                             **_settings_ctx(cfg, kept, error)), 400
            await tl_config.save(db, new)
            await set_setting(db, "timeline.retention_days", retention)
    await audit_request("settings.saved", detail={"section": "timeline"})
    return redirect(url_for("timeline.settings_page"))