"""routes_templates.py — WAVE 23 item 7 (ruling R10, contract C12): the template doors.

    GET  /api/v1/templates?table=<page key>   what can be applied HERE
    POST /api/v1/templates/{key}/apply {table}  apply it, to the CALLING USER's own views

Both session-gated. Neither is public and neither is admin-only: applying a template writes the
caller's PERSONAL saved views, which is something every user does to their own workspace all day
(`table_store.save_view(..., shared=False)`). The registry itself is platform-curated code
(`platform/core/view_templates.py`) — R10 explicitly rules out an end-user authoring UI this
wave, so there is no write door for the registry at all.

⛔ THE WALL IS THE SAME PREDICATE THE NAV USES, per topic, and it is applied before anything is
read or written:
  · `ut_*` — `user_tables.may_open` (creator, admin, or a share grant), exactly as
    `routes_tables._defn_or_refuse` does. `session.require` would 403 every ut key, because a
    user table is deliberately not a module (the split `/nav/schema/{key}` already makes).
  · a built-in topic — `session.require(key)`, the module grant.
A key that is neither is a 404 with the same sentence for both: this route is not a directory of
what exists.

⚠ REFUSE, NEVER PARTIALLY APPLY. `view_templates.missing_columns` runs against the TARGET's live
contract, and a template naming a column the target does not have comes back 400 with the
columns listed. The alternative — writing the views anyway — is the `_seed_wave17` failure
verbatim: `clean_filter_tree` DROPS a leaf on an unknown column, and a view whose only condition
was dropped shows EVERY row under a name that promises a shortlist.
"""
import uuid

from fastapi import APIRouter, Body, Depends

from deps import Session, err, perms, require_session

router = APIRouter(prefix="/api/v1")


def _templates():
    import core.view_templates as view_templates
    return view_templates


def _target_or_refuse(session, table_key):
    """`(field_keys, source_label)` for a table this session may open — or a refusal.

    The field keys are the LIVE contract, read the same way each topic's own reader reads it, so
    a template can never be offered against a column list this end assembled by hand.
    """
    key = str(table_key or '').strip()
    if not key:
        raise err(400, "bad_request", "no database was named")
    if key.startswith('ut_'):
        import core.user_tables as user_tables
        defn = user_tables.get(key, st=session.runtime)
        if not defn:
            raise err(404, "unknown_table", "that database does not exist")
        if not user_tables.may_open(key, session.uname, session.admin, st=session.runtime):
            raise err(403, "forbidden", "that database belongs to another user")
        fields = [str(f.get('key')) for f in (defn.get('fields') or []) if f.get('key')]
        # A user table has no fixed topic. Its SOURCE label is left blank so `offer` gates on
        # columns alone — which is the honest answer for a table whose shape its owner decides,
        # and is exactly why the column test is the real contract (view_templates' own note).
        return fields, ''
    if key not in ('customer_data', 'product_data'):
        raise err(404, "unknown_table", "that database does not exist")
    session.require(key)
    import aios_grid
    if key == 'product_data':
        return [f['key'] for f in aios_grid.product_fields()], 'odoo_product'
    return [f['key'] for f in aios_grid.FIELDS], 'odoo_customer'


@router.get("/templates")
def list_templates(table: str = "", session: Session = Depends(require_session)):
    """What can be applied to THIS database. `{table, templates: [...]}`.

    Filtered by the target's real columns, so the picker cannot offer something the apply door
    would refuse — one predicate, two callers (`view_templates.offer` wraps
    `missing_columns`, which is the same function the POST below re-runs).
    """
    fields, source = _target_or_refuse(session, table)
    vt = _templates()
    return {"table": table, "templates": vt.offer(fields, source or None)}


@router.post("/templates/{key}/apply")
def apply_template(key: str, body: dict = Body(default=None),
                   session: Session = Depends(require_session)):
    """Apply a template to a database, as the CALLING USER's own saved views.

    IDEMPOTENT BY PINNED VIEW ID (`tpl_<template>_<suffix>`): a second click updates the same
    views rather than minting "Past due 2". ⚠ That matters more than it sounds — `save_view`
    de-duplicates NAMES by appending a number, so an unpinned id would make every re-apply a
    fresh copy and the store would fill with numbered near-duplicates nobody asked for.
    """
    body = body if isinstance(body, dict) else {}
    fields, _source = _target_or_refuse(session, body.get("table"))
    vt = _templates()
    tpl = vt.get(key)
    if not tpl:
        raise err(404, "unknown_template", "that template does not exist")
    missing = vt.missing_columns(tpl, fields)
    if missing:
        # NAMED, not counted. "3 columns are missing" is a sentence the reader cannot act on;
        # the column keys are what tells them this is the wrong database for this template.
        raise err(400, "missing_columns",
                  "this database does not have the columns that template needs: "
                  + ", ".join(missing))
    ws_key = vt.workspace_key(body.get("table"))
    if not ws_key:
        raise err(404, "unknown_table", "that database does not exist")
    if not session.runtime.available():
        raise err(503, "store_unavailable",
                  "the tenant store is unavailable — nothing was applied")
    import core.table_store as table_store
    ops = table_store.make(ws_key, st=session.runtime)
    applied = []
    for view in tpl.get('views') or ():
        # ⛔ A COPY PER APPLY, and `createdBy` STAMPED HERE. The registry's dicts are module-level
        # — mutating one would write this caller's username into the template every other tenant
        # then reads, which is a cross-tenant leak with no symptom until two people apply the
        # same template. Same invariant `routes_nav`'s in-place merge documents from the other
        # side.
        payload = dict(view)
        payload['config'] = dict(view.get('config') or {})
        payload['createdBy'] = session.uname
        saved = ops.save_view(session.uname, payload, shared=False)
        applied.append({"id": payload['id'], "name": saved.get('name') or payload['name']})

    alert_id = None
    if tpl.get('alert') and applied:
        # The template's own view, watched. `core.alerts.create` stores the view BY ID rather
        # than a copy of its filter tree, so an alert made here keeps meaning "tell me about
        # this view" even after its owner edits it.
        topic = ('product' if body.get("table") == 'product_data'
                 else 'customer' if body.get("table") == 'customer_data'
                 else str(body.get("table")))
        try:
            import core.alerts as alerts
            alert_id = f"al_{uuid.uuid4().hex[:12]}"
            alerts.create(alert_id, view_id=applied[0]["id"], topic=topic,
                          owner=session.uname, label=applied[0]["name"],
                          st=session.runtime)
        except Exception:
            # ⚠ THE VIEWS ARE ALREADY WRITTEN AND THAT IS THE POINT: a failed alert must not
            # un-apply a template that worked. The response says which half landed rather than
            # reporting a total failure over a partial success.
            alert_id = None
    return {"key": key, "table": body.get("table"), "views": applied,
            "alert": alert_id, "alerted": bool(alert_id)}