"""Private, deterministic aggregation for comprehensive settlement previews."""
from __future__ import annotations

from datetime import date

from .shared import CASHFLOW_KIND_SQL

_AGGREGATION_VERSION = "comprehensive-v1"
_SNAPSHOT_SCHEMA_VERSION = 1
_ALLOWED_KINDS = {"income", "expense", "excluded"}


def _normalize_cashflow_policy(payload: dict) -> dict:
    if not isinstance(payload, dict) or set(payload) - {"savings_categories", "category_decisions"}:
        raise ValueError("cashflow policy must contain only supported keys")
    savings = payload.get("savings_categories", [])
    decisions = payload.get("category_decisions", [])
    if not isinstance(savings, list) or not isinstance(decisions, list):
        raise ValueError("policy categories and decisions must be lists")
    def pair(row, required):
        if not isinstance(row, dict) or set(row) != required:
            raise ValueError("invalid category policy entry")
        if any(not isinstance(row[k], str) for k in ("category", "subcategory")):
            raise ValueError("category fields must be strings")
        return row["category"], row["subcategory"]
    normalized_savings = [pair(x, {"category", "subcategory"}) for x in savings]
    if len(set(normalized_savings)) != len(normalized_savings):
        raise ValueError("duplicate savings category")
    normalized_decisions = []
    for row in decisions:
        cat, sub = pair(row, {"category", "subcategory", "cashflow_kind", "reason"})
        kind, reason = row["cashflow_kind"], row["reason"]
        if not isinstance(kind, str) or kind not in _ALLOWED_KINDS:
            raise ValueError("invalid cashflow decision kind")
        if not isinstance(reason, str) or not reason.strip():
            raise ValueError("decision reason must be nonempty")
        normalized_decisions.append((cat, sub, kind, reason))
    keys = [(x[0], x[1]) for x in normalized_decisions]
    if len(set(keys)) != len(keys):
        raise ValueError("duplicate category decision")
    return {"savings_categories": [{"category": c, "subcategory": s} for c, s in sorted(normalized_savings)],
            "category_decisions": [{"category": c, "subcategory": s, "cashflow_kind": k, "reason": r}
                                   for c, s, k, r in sorted(normalized_decisions)]}


def _review_cashflow(conn, month: str, policy: dict) -> dict:
    policy = _normalize_cashflow_policy(policy)
    start = date.fromisoformat(month + "-01")
    end = date(start.year + (start.month == 12), 1 if start.month == 12 else start.month + 1, 1)
    rows = conn.execute(f"""SELECT t.id,t.transaction_date,t.type,t.amount,t.currency,t.category,t.subcategory,
                 {CASHFLOW_KIND_SQL} AS originalcashflow_kind, lc.cashflow_kind AS category_cashflow_kind,
                 lc.active AS category_active
          FROM transactions t LEFT JOIN ledger_categories lc
            ON lc.category=t.category AND lc.subcategory=t.subcategory
          WHERE t.status='active' AND t.transaction_date>=? AND t.transaction_date<?
          ORDER BY t.transaction_date,t.id""", (start.isoformat(), end.isoformat())).fetchall()
    savings = {(x["category"], x["subcategory"]) for x in policy["savings_categories"]}
    decisions = {(x["category"], x["subcategory"]): x for x in policy["category_decisions"]}
    grouped, source, blockers = {}, [], []
    income = expense = 0
    for row in rows:
        t = dict(row)
        original = t["originalcashflow_kind"]
        pair = (t["category"], t["subcategory"])
        decision = decisions.get(pair)
        typ, catkind = t["type"], original
        amount = t["amount"]
        raw_valid = isinstance(amount, int) and not isinstance(amount, bool)
        reason = None
        # Explicit movement classes are immutable exclusions; investment is only selected by pair.
        general_transfer = catkind == "transfer" or (typ == "transfer" and catkind != "investment")
        initial_adjustment = typ == "adjustment"
        explicit_exclusion = decision and decision["cashflow_kind"] == "excluded"
        kind = "excluded"
        applied = amount if raw_valid else None
        if general_transfer or initial_adjustment or catkind in {"exclude", "transfer"} or explicit_exclusion:
            kind = "excluded"
        elif typ == "refund":
            if catkind in {"expense", "debt_payment"} or pair in savings or (decision and decision["cashflow_kind"] == "expense"):
                kind, applied = "expense", -amount if raw_valid else None
            else:
                reason = "refund requires an expense classification or explicit expense decision"
        elif catkind == "investment":
            if pair in savings:
                kind = "expense"
            else:
                kind = "excluded"
        elif catkind == "debt_payment":
            kind = "expense"
        elif catkind in {"income", "expense"}:
            kind = catkind
        elif decision and decision["cashflow_kind"] in {"income", "expense"}:
            kind = decision["cashflow_kind"]
        else:
            reason = "unknown cashflow classification requires an explicit decision"
        if not raw_valid and kind != "excluded":
            reason = "transaction amount is not an integer"
        if reason:
            blockers.append({"transaction_id": t["id"], "reason": reason})
            kind, applied = "unknown", None
        if kind != "excluded" and t["currency"].upper() != "KRW":
            blockers.append({"transaction_id": t["id"], "reason": "non-KRW currency requires FX review"})
            applied = None
        provenance = "category" if t["category_active"] else "fallback"
        evidence = {k: t[k] for k in ("id", "transaction_date", "type", "amount", "currency", "category", "subcategory")}
        evidence.update(originalcashflow_kind=original, cashflow_kind=kind, applied_amount=applied,
                        decision=decision, sourceprovenance=provenance,
                        category_cashflow_kind=t["category_cashflow_kind"], category_active=t["category_active"])
        source.append(evidence)
        if applied is None or kind not in {"income", "expense"}:
            if kind == "excluded" and applied is not None:
                key = (kind, pair[0], pair[1], t["currency"].upper())
                grp = grouped.setdefault(key, [0, 0]); grp[0] += applied; grp[1] += 1
            continue
        if t["currency"].upper() != "KRW":
            continue
        key = (kind, pair[0], pair[1], t["currency"].upper())
        grp = grouped.setdefault(key, [0, 0]); grp[0] += applied; grp[1] += 1
        if kind == "income": income += applied
        else: expense += applied
    items = [{"cashflow_kind": k, "category": c, "subcategory": s, "amount": v[0], "transaction_count": v[1], "currency": cur}
             for (k, c, s, cur), v in sorted(grouped.items())]
    return {"cashflow_policy": policy, "aggregation_version": _AGGREGATION_VERSION,
            "snapshot_schema_version": _SNAPSHOT_SCHEMA_VERSION, "income_total": income,
            "expense_total": expense, "net_cashflow": income-expense, "cashflow_items": items,
            "cashflow_blockers": blockers, "cashflow_warnings": [], "source_snapshot": {"transactions": source}}