"""Mantenimiento y reparacion de cards MBQL de Metabase."""

import copy
import time
import uuid

from .client import MetabaseClient


# ---------------------------------------------------------------------------
# Helpers internos compartidos
# ---------------------------------------------------------------------------


def _new_uuid() -> str:
    return str(uuid.uuid4())


def _field_name_of(node) -> tuple[str | None, str | None]:
    """Extrae (name, kind) de un node ['field'|'expression', meta, 'name']."""
    if isinstance(node, list) and len(node) >= 3 and node[0] in ("field", "expression"):
        nm = node[-1]
        if isinstance(nm, str):
            return nm, node[0]
    return None, None


# ---------------------------------------------------------------------------
# metabase_fix_null_ratio
# ---------------------------------------------------------------------------


def _analyze_stage_null_ratio(stage: dict) -> tuple[dict, dict]:
    """Detecta slots vulnerables al patron SUM(a-b)/SUM(b) en una stage MBQL.

    Devuelve:
        vulnerable: {slot_diff: (slot_a, slot_b, expr_name)}
        subtractions: {expr_name: (op_a_name, op_b_name)}
    """
    subtractions = {}
    for e in stage.get("expressions", []) or []:
        if not (isinstance(e, list) and len(e) == 4 and e[0] == "-"):
            continue
        meta = e[1] if isinstance(e[1], dict) else {}
        name = meta.get("lib/expression-name")
        if not name:
            continue
        a_name, a_kind = _field_name_of(e[2])
        b_name, b_kind = _field_name_of(e[3])
        if a_name and b_name and a_kind == "field" and b_kind == "field":
            subtractions[name] = (a_name, b_name)

    aggs = stage.get("aggregation", []) or []
    func_counts: dict[str, int] = {}
    sum_field_to_slot: dict[str, str] = {}
    sum_expr_to_slot: dict[str, str] = {}
    for agg in aggs:
        if not isinstance(agg, list) or not agg:
            continue
        func = agg[0]
        func_counts[func] = func_counts.get(func, 0) + 1
        slot = func if func_counts[func] == 1 else f"{func}_{func_counts[func]}"
        if func == "sum" and len(agg) >= 3:
            operand = agg[2]
            nm, kind = _field_name_of(operand)
            if kind == "field" and nm:
                sum_field_to_slot[nm] = slot
            elif kind == "expression" and nm:
                sum_expr_to_slot[nm] = slot

    vulnerable = {}
    for expr_name, slot_diff in sum_expr_to_slot.items():
        if expr_name not in subtractions:
            continue
        op_a, op_b = subtractions[expr_name]
        slot_a = sum_field_to_slot.get(op_a)
        slot_b = sum_field_to_slot.get(op_b)
        if slot_a and slot_b:
            vulnerable[slot_diff] = (slot_a, slot_b, expr_name)
    return vulnerable, subtractions


def _rewrite_field_refs(node, slot_map: dict):
    """Reemplaza recursivamente [field, meta, slot] donde slot in slot_map
    por [-, new_meta, [field, ..., slot_a], [field, ..., slot_b]]."""
    if isinstance(node, list):
        if (
            len(node) >= 3
            and node[0] == "field"
            and isinstance(node[-1], str)
            and node[-1] in slot_map
        ):
            slot_a, slot_b, _ = slot_map[node[-1]]
            base_type = (
                node[1].get("base-type", "type/Decimal")
                if isinstance(node[1], dict)
                else "type/Decimal"
            )
            return [
                "-",
                {"lib/uuid": _new_uuid()},
                ["field", {"base-type": base_type, "lib/uuid": _new_uuid()}, slot_a],
                ["field", {"base-type": base_type, "lib/uuid": _new_uuid()}, slot_b],
            ]
        return [_rewrite_field_refs(x, slot_map) for x in node]
    return node


def _fix_card_query(dq: dict) -> list[str]:
    """Aplica el fix in-place al dataset_query. Devuelve lista de cambios."""
    stages = dq.get("stages", [])
    changes = []
    for si, stage in enumerate(stages):
        vulnerable, subtractions = _analyze_stage_null_ratio(stage)
        if not vulnerable:
            continue

        preagg_names = set(subtractions.keys())
        new_exprs = []
        for e in stage.get("expressions", []) or []:
            if (
                isinstance(e, list)
                and len(e) == 4
                and e[0] == "-"
                and isinstance(e[1], dict)
                and e[1].get("lib/expression-name") in preagg_names
            ):
                new_exprs.append(e)
            else:
                new_exprs.append(_rewrite_field_refs(e, vulnerable))
        stage["expressions"] = new_exprs

        for sj in range(si + 1, len(stages)):
            for key in ("expressions", "aggregation", "breakout", "filters", "order-by", "fields"):
                if key in stages[sj]:
                    stages[sj][key] = [
                        _rewrite_field_refs(x, vulnerable) for x in stages[sj][key]
                    ]

        for slot, (sa, sb, ename) in vulnerable.items():
            changes.append(f"stage[{si}] {slot}=sum({ename!r}) -> ({sa} - {sb})")
    return changes


def metabase_fix_null_ratio(
    client: MetabaseClient,
    *,
    dry_run: bool = True,
    card_ids: list[int] | None = None,
) -> dict:
    """Detecta y repara el patron SUM(a-b)/SUM(b) en cards MBQL de Metabase.

    El patron vulnerable ocurre cuando una agregacion computa SUM(expr_resta)
    donde expr_resta es una resta pre-agg de dos campos. Si alguna fila tiene
    NULL, SUM(A-B) != SUM(A) - SUM(B). El fix reescribe las referencias
    post-agg al slot diferencia para usar (SUM(A) - SUM(B)) en su lugar.

    Solo procesa cards MBQL activas (type='query', no archivadas). Las cards
    SQL nativas o modelos se omiten silenciosamente.

    Args:
        client: Cliente Metabase autenticado.
        dry_run: Si True (default), escanea y reporta sin modificar nada.
                 Si False, aplica el fix via PUT /api/card/:id.
        card_ids: Lista de IDs a procesar. None = todas las cards MBQL activas.

    Returns:
        dict con campos:
            scanned (int): cards MBQL evaluadas.
            affected (int): cards donde se detecto el patron vulnerable.
            fixed (int): cards efectivamente actualizadas (0 si dry_run=True).
            errors (list[dict]): lista de {card_id, error} para fallos en PUT.

    Example:
        >>> from metabase import MetabaseClient, metabase_fix_null_ratio
        >>> c = MetabaseClient("https://metabase.example.com", "mb_apikey")
        >>> report = metabase_fix_null_ratio(c, dry_run=True)
        >>> print(report)
        {'scanned': 312, 'affected': 4, 'fixed': 0, 'errors': []}
        >>> # Para aplicar:
        >>> report = metabase_fix_null_ratio(c, dry_run=False)
    """
    all_cards = client.request("GET", "/api/card")

    if card_ids is not None:
        card_id_set = set(card_ids)
        all_cards = [c for c in all_cards if c.get("id") in card_id_set]

    mbql_cards = [
        c for c in all_cards
        if not c.get("archived", False)
        and isinstance(c.get("dataset_query"), dict)
        and c["dataset_query"].get("type") == "query"
        and isinstance(c["dataset_query"].get("query", {}).get("stages") if "query" in c["dataset_query"] else c["dataset_query"].get("stages"), list)
    ]

    # Metabase MBQL puede tener stages en dataset_query.query.stages (legacy)
    # o en dataset_query.stages (v2). Normalizar:
    def _get_stages(dq: dict) -> list | None:
        if isinstance(dq.get("stages"), list):
            return dq["stages"]
        q = dq.get("query", {})
        if isinstance(q.get("stages"), list):
            return q["stages"]
        return None

    affected_cards = []
    scanned = 0
    for card in all_cards:
        if card_ids is not None and card.get("id") not in set(card_ids):
            continue
        if card.get("archived", False):
            continue
        dq = card.get("dataset_query")
        if not isinstance(dq, dict):
            continue
        stages = _get_stages(dq)
        if stages is None:
            continue
        scanned += 1
        dq_copy = copy.deepcopy(dq)
        # Operar sobre el stages del objeto correcto
        target = dq_copy if isinstance(dq_copy.get("stages"), list) else dq_copy.get("query", {})
        changes = _fix_card_query(target)
        if changes:
            affected_cards.append((card, dq_copy, changes))

    fixed = 0
    errors: list[dict] = []

    if not dry_run:
        for card, dq_fixed, _changes in affected_cards:
            try:
                client.request("PUT", f"/api/card/{card['id']}", json={"dataset_query": dq_fixed})
                fixed += 1
            except Exception as exc:
                errors.append({"card_id": card["id"], "error": str(exc)[:200]})
            time.sleep(0.05)

    return {
        "scanned": scanned,
        "affected": len(affected_cards),
        "fixed": fixed,
        "errors": errors,
    }


# ---------------------------------------------------------------------------
# metabase_pair_n_n1_columns
# ---------------------------------------------------------------------------


def _slot_for_sum_field(stage: dict, target_field_name: str) -> str | None:
    """Devuelve el slot MBQL (ej: 'sum', 'sum_4') de sum(target_field) en la stage."""
    aggs = stage.get("aggregation", []) or []
    func_counts: dict[str, int] = {}
    for agg in aggs:
        if not isinstance(agg, list) or not agg:
            continue
        func = agg[0]
        func_counts[func] = func_counts.get(func, 0) + 1
        slot = func if func_counts[func] == 1 else f"{func}_{func_counts[func]}"
        if func == "sum" and len(agg) >= 3:
            nm, kind = _field_name_of(agg[2])
            if kind == "field" and nm == target_field_name:
                return slot
    return None


def _find_paired_slots(dq: dict, base_name: str) -> tuple[str | None, str | None]:
    """Busca (slot_base, slot_n1) para sum(base_name) y sum(base_name_1) en el MBQL."""
    for stage in (dq.get("stages") or []):
        if not stage.get("aggregation"):
            continue
        slot_n = _slot_for_sum_field(stage, base_name)
        slot_n1 = _slot_for_sum_field(stage, f"{base_name}_1")
        if slot_n and slot_n1:
            return slot_n, slot_n1
    return None, None


def _reorder_table_columns(
    cols: list[dict],
    slot_n: str,
    slot_n1: str,
) -> tuple[list[dict], bool, str]:
    """Habilita slot_n1 y lo reubica inmediatamente despues de slot_n.

    Returns:
        (new_cols, changed, reason)
    """
    cols = [dict(c) for c in cols]
    idx_n = next((i for i, c in enumerate(cols) if c.get("name") == slot_n), -1)
    if idx_n < 0:
        return cols, False, "slot_n no presente en table.columns"

    idx_n1 = next((i for i, c in enumerate(cols) if c.get("name") == slot_n1), -1)

    # Ya en posicion correcta y habilitada: no hay cambio
    if idx_n1 == idx_n + 1 and cols[idx_n1].get("enabled") is True:
        return cols, False, "ya en la posicion correcta y habilitado"

    if idx_n1 < 0:
        entry: dict = {"name": slot_n1, "enabled": True}
    else:
        entry = cols.pop(idx_n1)
        entry["enabled"] = True
        if idx_n1 < idx_n:
            idx_n -= 1

    insert_at = idx_n + 1
    cols.insert(insert_at, entry)
    return cols, True, "reubicado y habilitado"


def metabase_pair_n_n1_columns(
    client: MetabaseClient,
    *,
    dry_run: bool = True,
    card_ids: list[int] | None = None,
    base_field: str = "Valor_vendido",
) -> dict:
    """Habilita y posiciona la columna _1 junto a su par en cards tabla/pivot de Metabase.

    Para cards con display 'table' o 'pivot' que contienen agregaciones
    SUM(base_field) y SUM(base_field_1), busca la columna base_field_1 en
    visualization_settings.table.columns, la habilita (enabled=True) y la
    reubica inmediatamente despues de base_field para comparacion visual.

    Solo procesa cards con display 'table' o 'pivot' que tengan ambos slots
    y tengan table.columns definido en visualization_settings.

    Args:
        client: Cliente Metabase autenticado.
        dry_run: Si True (default), escanea y reporta sin modificar nada.
                 Si False, aplica el cambio via PUT /api/card/:id.
        card_ids: Lista de IDs a procesar. None = todas las cards activas.
        base_field: Nombre del campo base MBQL (sin sufijo _1). Por defecto
                    'Valor_vendido'. La funcion buscara sum(base_field) y
                    sum(base_field_1) en las agregaciones.

    Returns:
        dict con campos:
            scanned (int): cards con display table/pivot evaluadas.
            affected (int): cards donde se encontro el par y habia que mover.
            fixed (int): cards efectivamente actualizadas (0 si dry_run=True).
            skipped (int): cards ya correctas o sin table.columns.
            errors (list[dict]): lista de {card_id, error} para fallos en PUT.

    Example:
        >>> from metabase import MetabaseClient, metabase_pair_n_n1_columns
        >>> c = MetabaseClient("https://metabase.example.com", "mb_apikey")
        >>> report = metabase_pair_n_n1_columns(c, dry_run=True)
        >>> print(report)
        {'scanned': 45, 'affected': 3, 'fixed': 0, 'skipped': 42, 'errors': []}
        >>> # Con campo personalizado:
        >>> report = metabase_pair_n_n1_columns(c, dry_run=False, base_field="Importe")
    """
    all_cards = client.request("GET", "/api/card")

    tabular_displays = {"table", "pivot"}
    scanned = 0
    skipped = 0
    to_update: list[tuple[dict, list[dict], str, str]] = []

    for card in all_cards:
        if card_ids is not None and card.get("id") not in set(card_ids):
            continue
        if card.get("archived", False):
            continue
        if card.get("display") not in tabular_displays:
            continue
        dq = card.get("dataset_query")
        if not isinstance(dq, dict):
            continue

        slot_n, slot_n1 = _find_paired_slots(dq, base_field)
        if not (slot_n and slot_n1):
            continue

        scanned += 1
        vs = card.get("visualization_settings") or {}
        cols = vs.get("table.columns")
        if not isinstance(cols, list):
            skipped += 1
            continue

        new_cols, changed, _reason = _reorder_table_columns(cols, slot_n, slot_n1)
        if not changed:
            skipped += 1
            continue

        to_update.append((card, new_cols, slot_n, slot_n1))

    fixed = 0
    errors: list[dict] = []

    if not dry_run:
        for card, new_cols, _slot_n, _slot_n1 in to_update:
            new_vs = copy.deepcopy(card.get("visualization_settings") or {})
            new_vs["table.columns"] = new_cols
            try:
                client.request(
                    "PUT",
                    f"/api/card/{card['id']}",
                    json={"visualization_settings": new_vs},
                )
                fixed += 1
            except Exception as exc:
                errors.append({"card_id": card["id"], "error": str(exc)[:200]})
            time.sleep(0.05)

    return {
        "scanned": scanned,
        "affected": len(to_update),
        "fixed": fixed,
        "skipped": skipped,
        "errors": errors,
    }