"""REST routes for lessons — a transferable insight, retrievable by situation.

A lesson is a note with note_type='lesson' (see services/lessons.py). These
routes feed the web UI; the MCP tools (mcp/tools/lessons.py) are the
agent-facing surface. Both go through services/lessons.py, so the compose/parse
contract and the `data` mirror live in one place — the same division snippets
use, and for the same reason: two doors that each compose a lesson would
compose it two ways, and the document IS what ranks.

ACL (rule #78): reads and writes of a single lesson resolve through the
share-aware `get_lesson` / `can_write_note`, and writes are performed as the
OWNER so a shared editor isn't rejected by the owner-scoped service —
mirroring routes/snippets.py and routes/notes.py.

WHY THE TRIGGER IS A NAMED FIELD HERE TOO. The web editor could have posted a
body and let the service parse it. It doesn't, because the evidence behind
this kind (step 1) is that a trigger gets filled when a door ASKS for it by
name — the snippet corpus is at 100% on its trigger with no guard anywhere,
because a service composes the title from a parameter. A form that offered one
markdown box would be the option milestone 385 rejected, wearing a different
hat.
"""
import logging

from quart import Blueprint, jsonify, request

from scribe.auth import get_current_user_id, login_required
from scribe.routes.utils import not_found, parse_pagination
from scribe.services import dedup as dedup_svc
from scribe.services import knowledge as knowledge_svc
from scribe.services import lesson_rules as lesson_rules_svc
from scribe.services import lessons as lessons_svc
from scribe.services import systems as systems_svc
from scribe.services import trash as trash_svc
from scribe.services.access import (
    can_write_note,
    describe_provenance,
    label_shared_items,
)
from scribe.services.note_usage import attach_usage, record_pulled

logger = logging.getLogger(__name__)

lessons_bp = Blueprint("lessons", __name__, url_prefix="/api/lessons")


@lessons_bp.route("", methods=["GET"])
@login_required
async def list_lessons_route():
    """The kind enumerated, rather than only what a query resembles.

    Semantic search is how a lesson REACHES a session; this is how a person
    sees what exists at all. Each row carries its trigger, because a list of
    lessons without them is a list of claims with the half that says when each
    one matters left off.
    """
    uid = get_current_user_id()
    q = request.args.get("q") or None
    tag = request.args.get("tag", "")
    try:
        project_id = int(request.args.get("project_id", 0) or 0) or None
    except (TypeError, ValueError):
        project_id = None
    limit, offset = parse_pagination(default_limit=24, max_limit=100)

    # The lessons nobody has answered "which rule?" for (#4631). A listing,
    # so it does not combine with a search — the MCP door says the same.
    if request.args.get("unjudged") in ("1", "true"):
        if q:
            return jsonify({"error": "unjudged is a listing; drop q"}), 400
        items, total = await lesson_rules_svc.list_unjudged(
            uid, tag=tag, project_id=project_id, limit=limit, offset=offset,
        )
    else:
        items, total = await knowledge_svc.query_knowledge(
            user_id=uid,
            note_type=lessons_svc.LESSON_NOTE_TYPE,
            tags=[tag] if tag else [],
            sort="modified",
            q=q,
            limit=limit,
            offset=offset,
            project_id=project_id,
        )
    items = await label_shared_items(uid, items)
    # One aggregate for the whole page — a per-row lookup would be N+1 by
    # construction. Every row gets the key, zero-filled, so the UI renders
    # "never surfaced" rather than treating a missing field as a state.
    #
    # Lessons were the one kind collecting this and showing it nowhere (#4196).
    # The counts matter more here than on a snippet: the promotion question a
    # lesson eventually raises — does this bind? — is answered by repeatedly
    # surfaced AND repeatedly opened, and the far commoner reading of the same
    # row is that the trigger fires on the wrong situation, which `update_lesson`
    # exists to fix.
    await attach_usage(items)
    return jsonify({"lessons": items, "total": total})


@lessons_bp.route("/taught-by/<int:record_id>", methods=["GET"])
@login_required
async def lessons_taught_by_route(record_id: int):
    """The lessons drawn FROM one record — the reverse of `learned_from`.

    Registered ABOVE the `/<int:lesson_id>` routes on purpose: Quart matches
    in registration order, and `taught-by` would otherwise never be reached
    if the converter ever widened. The same ordering snippets' `/duplicates`
    route documents.

    This is the direction that gets forgotten. A reader opening an old issue
    wants to know what was learned from it, and without this the relation is
    only navigable from the lesson's side.
    """
    uid = get_current_user_id()
    notes = await lessons_svc.lessons_taught_by(uid, record_id)
    return jsonify({
        "lessons": [lessons_svc.lesson_to_dict(n) for n in notes],
        "taught_by": record_id,
    })


@lessons_bp.route("", methods=["POST"])
@login_required
async def create_lesson_route():
    uid = get_current_user_id()
    data = await request.get_json() or {}
    what = (data.get("what") or "").strip()
    when_to_apply = (data.get("when_to_apply") or "").strip()
    if not what:
        return jsonify({"error": "what is required"}), 400
    # The trigger is not optional at this door even though the service will
    # store a lesson without one. A lesson with no trigger saves, reads
    # correctly in every listing, and never surfaces — there is nothing to
    # notice afterwards, which is exactly why the form has to refuse it here
    # rather than leave the writer a record that looks finished.
    if not when_to_apply:
        return jsonify({
            "error": "when_to_apply is required",
            "detail": (
                "A lesson is found by the SITUATION it applies to. Without a "
                "trigger it still saves and still reads correctly, and it "
                "never reaches anyone — so it is refused here rather than "
                "stored as a record that looks finished."
            ),
        }), 400

    project_id = data.get("project_id") or None
    learned_from = data.get("learned_from") or []
    # The rules this lesson is an instance of (milestone 440). Validated before
    # anything is written, as the MCP door does, so a bad id saves nothing.
    no_rule = (data.get("no_rule") or "").strip()
    try:
        linked = await lesson_rules_svc.require_rules(uid, data.get("rule_ids") or [])
        lesson_rules_svc.require_one_answer(linked, no_rule)
    except ValueError as exc:
        return jsonify({"error": str(exc)}), 400

    # The same near-duplicate gate the MCP create path applies. Two lessons
    # under one trigger compete in a single ranked list for one reserved slot,
    # so the duplicate does not merely clutter — it displaces.
    if not data.get("force"):
        title, body = lessons_svc.lesson_document(
            what, when_to_apply, data.get("insight", ""), learned_from,
        )
        dup = await dedup_svc.find_duplicate_note(
            uid, title, body,
            project_id=project_id,
            is_task=False,
            note_type=lessons_svc.LESSON_NOTE_TYPE,
            data=lessons_svc.compose_data(what, when_to_apply),
        )
        if dup is not None:
            return jsonify(dedup_svc.duplicate_response(dup, "lesson")), 409

    note = await lessons_svc.create_lesson(
        uid,
        what=what,
        when_to_apply=when_to_apply,
        insight=data.get("insight", ""),
        learned_from=learned_from,
        tags=data.get("tags"),
        project_id=project_id,
    )
    if data.get("system_ids") is not None:
        await systems_svc.set_record_systems(uid, note.id, data["system_ids"])
    if linked:
        await lesson_rules_svc.set_lesson_rules(uid, note.id, linked)
    elif no_rule:
        await lesson_rules_svc.set_no_rule(uid, note.id, no_rule)
    out = lessons_svc.lesson_to_dict(note)
    if no_rule:
        group = await lesson_rules_svc.convergence_for(uid, note.id)
        if group:
            out["convergence"] = group
    out["systems"] = [
        s.to_dict() for s in await systems_svc.list_record_systems(uid, note.id)
    ]
    await lesson_rules_svc.attach_lesson_rules(uid, [out])
    # The same offer the MCP door makes, so the form can show the rules to
    # judge against while the writer still has the situation in mind.
    if not linked and not no_rule:
        candidates = await lesson_rules_svc.rule_candidates(
            uid, what, when_to_apply, project_id,
        )
        if candidates is not None:
            out["rule_candidates"] = candidates
    return jsonify(out), 201


@lessons_bp.route("/<int:lesson_id>", methods=["GET"])
@login_required
async def get_lesson_route(lesson_id: int):
    uid = get_current_user_id()
    note = await lessons_svc.get_lesson(uid, lesson_id)
    if note is None:
        return not_found("Lesson")
    out = lessons_svc.lesson_to_dict(note)
    # As the OWNER: a shared reader isn't scoped to the owner's project, so
    # their own id would come back empty (the write-as-owner pattern this
    # module already uses, read side).
    out["systems"] = [
        s.to_dict()
        for s in await systems_svc.list_record_systems(note.user_id, lesson_id)
    ]
    # Resolved, not bare ids: "#4181" on a page tells a reader nothing about
    # whether it is worth opening, and the provenance is the point of a lesson.
    out["learned_from_records"] = await lessons_svc.source_records(
        uid, out["learned_from"]
    )
    out.update(await describe_provenance(uid, note))
    await attach_usage([out])
    await lesson_rules_svc.attach_lesson_rules(uid, [out])
    # Opening the detail view IS a pull — the operator chose to look. Tagged
    # apart from the MCP sources so "an agent was handed it" and "a human read
    # it" stay distinguishable; they mean different things for pruning (#2085).
    record_pulled(user_id=uid, note_id=lesson_id, source="rest_lesson")
    return jsonify(out)


@lessons_bp.route("/<int:lesson_id>", methods=["PATCH"])
@login_required
async def update_lesson_route(lesson_id: int):
    uid = get_current_user_id()
    note = await lessons_svc.get_lesson(uid, lesson_id)
    if note is None:
        return not_found("Lesson")
    if not await can_write_note(uid, lesson_id):
        return jsonify({"error": "Permission denied"}), 403
    owner_uid = note.user_id
    data = await request.get_json() or {}

    # Partial update: only keys present in the payload change, and the service
    # re-composes title, body and mirror from the merged set — so a form that
    # sends one field cannot leave the halves of the document disagreeing.
    kwargs = {
        k: data[k]
        for k in ("what", "when_to_apply", "insight", "learned_from", "tags")
        if k in data
    }
    # An empty trigger would save and silently stop the lesson surfacing, so
    # clearing it is refused for the same reason creating without one is.
    if "when_to_apply" in kwargs and not (kwargs["when_to_apply"] or "").strip():
        return jsonify({
            "error": "when_to_apply cannot be cleared",
            "detail": (
                "A lesson with no trigger never surfaces, and nothing about "
                "the stored record would show it. Rewrite the trigger rather "
                "than emptying it."
            ),
        }), 400

    linked = None
    no_rule = (data.get("no_rule") or "").strip()
    try:
        if data.get("rule_ids") is not None:
            linked = await lesson_rules_svc.require_rules(uid, data["rule_ids"])
        lesson_rules_svc.require_one_answer(linked, no_rule)
    except ValueError as exc:
        return jsonify({"error": str(exc)}), 400

    updated = await lessons_svc.update_lesson(owner_uid, lesson_id, **kwargs)
    if updated is None:
        return not_found("Lesson")
    if linked is not None:
        # The CALLER, for the reason system_ids below uses it: the rules named
        # must be ones the person making the edit can read.
        await lesson_rules_svc.set_lesson_rules(uid, lesson_id, linked)
    if no_rule:
        await lesson_rules_svc.set_no_rule(uid, lesson_id, no_rule)
    if data.get("system_ids") is not None:
        # The CALLER, not owner_uid (#4249). `set_record_systems` runs its own
        # `can_write_note` and links only Systems the acting user can read;
        # handing it the owner makes that check trivially pass and filters by
        # the owner's visibility instead. The caller's write permission is
        # already established above, so this neither loosens nor tightens who
        # may edit — it decides WHOSE reach the tagging uses (#47).
        await systems_svc.set_record_systems(uid, lesson_id, data["system_ids"])
    out = lessons_svc.lesson_to_dict(updated)
    if no_rule:
        # The same nudge the MCP door gives (#4634): this answer may complete
        # a group of no-rule lessons in one situation.
        group = await lesson_rules_svc.convergence_for(uid, lesson_id)
        if group:
            out["convergence"] = group
    out["systems"] = [
        s.to_dict()
        for s in await systems_svc.list_record_systems(owner_uid, lesson_id)
    ]
    await lesson_rules_svc.attach_lesson_rules(uid, [out])
    return jsonify(out)


@lessons_bp.route("/<int:lesson_id>/rules/<int:rule_id>", methods=["PUT"])
@login_required
async def judge_lesson_link_route(lesson_id: int, rule_id: int):
    """Confirm or reject one lesson→rule link — the REST twin of the MCP
    `judge_lesson_link`. Body: {"verdict": "confirm" | "reject", "note": "…"}."""
    uid = get_current_user_id()
    data = await request.get_json() or {}
    try:
        link = await lesson_rules_svc.judge_link(
            uid, lesson_id, rule_id, data.get("verdict", ""), data.get("note", ""),
        )
    except PermissionError:
        return jsonify({"error": "Permission denied"}), 403
    except ValueError as exc:
        return jsonify({"error": str(exc)}), 400
    return jsonify(link)


@lessons_bp.route("/<int:lesson_id>", methods=["DELETE"])
@login_required
async def delete_lesson_route(lesson_id: int):
    """Trash, not erase — recoverable from the trash like every other kind."""
    uid = get_current_user_id()
    note = await lessons_svc.get_lesson(uid, lesson_id)
    if note is None:
        return not_found("Lesson")
    if not await can_write_note(uid, lesson_id):
        return jsonify({"error": "Permission denied"}), 403
    batch_id = await trash_svc.delete(note.user_id, "note", lesson_id)
    if batch_id is None:
        return not_found("Lesson")
    return jsonify({"deleted": lesson_id, "deleted_batch_id": batch_id})