"""Rules Engine: pure expansion of a BOQ item into activity + dependency drafts.

Template-driven (NO hardcoded if/else on procurement_type or category). Reads
activity_templates + dependency_templates via a repo; never writes to the DB.
"""

import re

from app.rules.errors import NoTemplateError
from app.rules.templates_repo import TemplatesRepo
from app.rules.types import ActivityDraft, BOQItemInput, DependencyDraft, ExpandResult

_PLACEHOLDER = re.compile(r"\{(\w+)\}")


def _render_template(template: str, boq: BOQItemInput) -> str:
    return _PLACEHOLDER.sub(lambda m: str(getattr(boq, m.group(1), "") or ""), template)


def _num(value) -> float | None:
    return None if value is None else float(value)


def expand(boq: BOQItemInput, repo: TemplatesRepo) -> ExpandResult:
    templates = repo.find_activity_templates(
        category_id=boq.category_id,
        procurement_type=boq.procurement_type,
        active=True,
    )
    if not templates:
        raise NoTemplateError(boq.category_id, boq.procurement_type)

    override_effort = boq.metadata.get("override_effort_days")
    override_lead = boq.metadata.get("override_lead_time_days")

    activities: list[ActivityDraft] = [
        ActivityDraft(
            boq_item_id=boq.id,
            template_id=t["id"],
            kind=t["kind"],
            name=_render_template(t["name_template"], boq),
            effort_days=_num(override_effort) if override_effort is not None else _num(t["default_effort_days"]),
            lead_time_days=_num(override_lead) if override_lead is not None else _num(t["default_lead_time_days"]),
            clock=t["clock"],
            noisy=bool(t["noisy"]),
            responsibility=(
                boq.procurement_responsibility if t["kind"] == "PROCUREMENT" else "CONTRACTOR"
            ),
            _tag=f"{boq.id}:{t['kind']}",
        )
        for t in templates
    ]

    dep_rows = repo.find_dependency_templates(category_id=boq.category_id, active=True)
    dependencies: list[DependencyDraft] = []
    for d in dep_rows:
        pred = next((a for a in activities if a.kind == d["predecessor_kind"]), None)
        succ = next((a for a in activities if a.kind == d["successor_kind"]), None)
        if pred and succ:
            dependencies.append(
                DependencyDraft(
                    predecessor_tag=pred._tag,
                    successor_tag=succ._tag,
                    dep_type=d["dep_type"],
                    lag_days=float(d["lag_days"]),
                    origin="TEMPLATE",
                )
            )

    return ExpandResult(activities=activities, dependencies=dependencies)