from pypdf import PdfReader

def discover_fields(pdf_path: str) -> list[dict]:
    """
    Introspect a PDF and return all fillable AcroForm fields.
    Handles any form of AcroForm structure.
    """
    reader = PdfReader(pdf_path)
    
    # Try multiple methods to get fields
    fields = None
    
    # Method 1: Try get_fields() first
    try:
        fields = reader.get_fields()
    except Exception as e:
        print(f"get_fields() failed: {e}")
        fields = None
    
    # Method 2: Try to get fields from AcroForm directly
    if not fields:
        try:
            if "/AcroForm" in reader.trailer["/Root"]:
                acroform = reader.trailer["/Root"]["/AcroForm"]
                if "/Fields" in acroform:
                    fields = {}
                    field_array = acroform["/Fields"]
                    for field_ref in field_array:
                        try:
                            field_obj = field_ref.get_object()
                            field_name = field_obj.get("/T", "")
                            if field_name:
                                fields[field_name] = field_obj
                        except Exception as e:
                            print(f"Error processing field: {e}")
                            continue
        except Exception as e:
            print(f"Direct AcroForm access failed: {e}")
            fields = None
    
    # Method 3: Try to get fields from page annotations
    if not fields:
        try:
            fields = {}
            for page in reader.pages:
                if "/Annots" in page:
                    for annot in page["/Annots"]:
                        try:
                            annot_obj = annot.get_object()
                            if "/Subtype" in annot_obj and annot_obj["/Subtype"] == "/Widget":
                                field_name = annot_obj.get("/T", "")
                                if field_name and field_name not in fields:
                                    fields[field_name] = annot_obj
                        except Exception as e:
                            print(f"Error processing annotation: {e}")
                            continue
        except Exception as e:
            print(f"Page annotation access failed: {e}")
            fields = None

    if not fields:
        return []

    result = []
    for field_name, field_obj in fields.items():
        try:
            field_type = field_obj.get("/FT", "")
            options = []

            # /Ch = choice field (select/dropdown)
            if field_type == "/Ch":
                opt = field_obj.get("/Opt", [])
                if opt:
                    options = [o if isinstance(o, str) else o[1] for o in opt]

            result.append({
                "field": field_name,
                "label": field_name.replace("_", " ").title(),
                "type": _map_field_type(field_type, field_obj),
                "required": False,
                "options": options if options else None
            })
        except Exception as e:
            print(f"Error processing field {field_name}: {e}")
            continue

    return result

def _map_field_type(ft: str, field_obj: dict) -> str:
    mapping = {
        "/Tx": "string",
        "/Btn": "boolean",
        "/Ch": "select",
        "/Sig": "string"
    }
    base = mapping.get(ft, "string")

    # Check if it's a date field by name hint
    field_name = field_obj.get("/T", "").lower()
    if any(hint in field_name for hint in ["date", "fecha", "birth", "nacimiento"]):
        return "date"

    return base