import ast
import logging
from llvmlite import ir
from .type_deducer import ctypes_to_ir

logger = logging.getLogger(__name__)

# TODO: Shall we allow the following syntax:
# struct MyStruct:
#     field1: int
#     field2: str(32)
# Where int is mapped to c_uint64?
# Shall we just int64, int32 and uint32 similarly?


def structs_proc(tree, module, chunks):
    """ Process all class definitions to find BPF structs """
    structs_sym_tab = {}
    for cls_node in chunks:
        if is_bpf_struct(cls_node):
            print(f"Found BPF struct: {cls_node.name}")
            struct_info = process_bpf_struct(cls_node, module)
            structs_sym_tab[cls_node.name] = struct_info
    return structs_sym_tab


def is_bpf_struct(cls_node):
    return any(
        isinstance(decorator, ast.Name) and decorator.id == "struct"
        for decorator in cls_node.decorator_list
    )


def process_bpf_struct(cls_node, module):
    """ Process a single BPF struct definition """

    field_names, field_types = parse_struct_fields(cls_node)
    total_size = calc_struct_size(field_types)
    struct_type = ir.LiteralStructType(field_types)
    logger.info(f"Created struct {cls_node.name} with fields {field_names}")
    return {
        "type": struct_type,
        "fields": {name: idx for idx, name in enumerate(field_names)},
        "size": total_size,
        "field_types": field_types,
    }


def parse_struct_fields(cls_node):
    """ Parse fields of a struct class node """
    field_names = []
    field_types = []

    for item in cls_node.body:
        if isinstance(item, ast.AnnAssign) and \
           isinstance(item.target, ast.Name):
            field_names.append(item.target.id)
            field_types.append(get_type_from_ann(item.annotation))
        else:
            logger.error(f"Unsupported struct field: {ast.dump(item)}")
            raise TypeError(f"Unsupported field in {ast.dump(cls_node)}")
    return field_names, field_types


def get_type_from_ann(annotation):
    """ Convert an AST annotation node to an LLVM IR type for struct fields"""
    if isinstance(annotation, ast.Call) and \
       isinstance(annotation.func, ast.Name):
        if annotation.func.id == "str":
            # Assumes constant integer argument
            length = annotation.args[0].value
            return ir.ArrayType(ir.IntType(8), length)
    elif isinstance(annotation, ast.Name):
        return ctypes_to_ir(annotation.id)

    raise TypeError(f"Unsupported annotation type: {ast.dump(annotation)}")


def calc_struct_size(field_types):
    """ Calculate total size of the struct with alignment and padding """
    curr_offset = 0
    for ftype in field_types:
        if isinstance(ftype, ir.IntType):
            fsize = ftype.width // 8
            alignment = fsize
        elif isinstance(ftype, ir.ArrayType):
            fsize = ftype.count * (ftype.element.width // 8)
            alignment = ftype.element.width // 8
        elif isinstance(ftype, ir.PointerType):
            fsize = 8
            alignment = 8
        else:
            raise TypeError(f"Unsupported field type: {ftype}")

        padding = (alignment - (curr_offset % alignment)) % alignment
        curr_offset += padding + fsize

    final_padding = (8 - (curr_offset % 8)) % 8
    return curr_offset + final_padding