"""Shared EAV flattening utility.

Every endpoint that returns materials (``material_attribute_values``) or
line items (``line_item_specs``) with expand uses this single function to
produce the contract shape:

    [{"attribute_key", "label", "data_type", "value", "unit"}]

value extraction:
    number/integer -> value_number (integer cast for `integer`)
    string/enum    -> value_string
    boolean        -> value_boolean
    date           -> value_date (ISO string)

unit resolution:
    prefer row.unit_id_at_time when available (prefer_unit_id_at_time=True),
    else fall back to attribute_definitions.unit_id.
"""
from app.models.catalog import AttributeDefinition, MaterialAttributeValue
from app.models.procurement import LineItemSpec

_EAVRow = MaterialAttributeValue | LineItemSpec


def _extract_value(ad: AttributeDefinition, row: _EAVRow):
    data_type = ad.data_type
    if data_type in ("number", "integer"):
        if row.value_number is None:
            return None
        return int(row.value_number) if data_type == "integer" else float(row.value_number)
    if data_type in ("string", "enum"):
        return row.value_string
    if data_type == "boolean":
        return row.value_boolean
    if data_type == "date":
        return row.value_date.isoformat() if row.value_date is not None else None
    return None


def _resolve_unit(row: _EAVRow, ad: AttributeDefinition, unit_map: dict, prefer_unit_id_at_time: bool):
    unit_id = None
    if prefer_unit_id_at_time and hasattr(row, "unit_id_at_time") and row.unit_id_at_time is not None:
        unit_id = row.unit_id_at_time
    elif ad.unit_id is not None:
        unit_id = ad.unit_id
    unit = unit_map.get(unit_id) if unit_id is not None else None
    if unit is None:
        return None
    return {"id": unit.id, "code": unit.code}


def flatten_eav_values(
    rows: list[_EAVRow],
    attr_defs_map: dict,
    unit_map: dict,
    prefer_unit_id_at_time: bool = True,
    include_definition_id: bool = False,
    include_data_type: bool = True,
) -> list[dict]:
    """Flatten typed EAV rows into the contract's `value`/`unit` shape."""
    result: list[dict] = []
    for row in rows:
        ad = attr_defs_map[row.attribute_definition_id]
        item: dict = {}
        if include_definition_id:
            item["attribute_definition_id"] = str(row.attribute_definition_id)
        item["attribute_key"] = ad.attribute_key
        item["label"] = ad.label
        if include_data_type:
            item["data_type"] = ad.data_type
        item["value"] = _extract_value(ad, row)
        item["unit"] = _resolve_unit(row, ad, unit_map, prefer_unit_id_at_time)
        result.append(item)
    return result