"""
This module generates source code based on the parsed AST

It's intented to be a "any color, as long as it's black" kind of renderer
"""
from typing import Any, Generator

from . import ourlang
from .type3.types import Type3, TypeApplication_Struct
from .type5 import typeexpr as type5typeexpr


def phasm_render(inp: ourlang.Module[Any]) -> str:
    """
    Public method for rendering a Phasm module into Phasm code
    """
    return module(inp)

Statements = Generator[str, None, None]

def type3(inp: Type3) -> str:
    """
    Render: type's name
    """
    return inp.name

def type5(mod: ourlang.Module[Any], inp: type5typeexpr.TypeExpr) -> str:
    """
    Render: type's name
    """
    return mod.build.type5_name(inp)

def struct_definition(inp: ourlang.StructDefinition) -> str:
    """
    Render: TypeStruct's definition
    """
    assert isinstance(inp.struct_type3.application, TypeApplication_Struct)

    result = f'class {inp.struct_type3.name}:\n'
    for mem, typ in inp.struct_type3.application.arguments:
        result += f'    {mem}: {type3(typ)}\n'

    return result

def constant_definition(inp: ourlang.ModuleConstantDef) -> str:
    """
    Render: Module Constant's  definition
    """
    return f'{inp.name}: {type3(inp.type3)} = {expression(inp.constant)}\n'

def expression(inp: ourlang.Expression) -> str:
    """
    Render: A Phasm expression
    """
    if isinstance(inp, ourlang.ConstantPrimitive):
        # Floats might not round trip if the original constant
        # could not fit in the given float type
        return str(inp.value)

    if isinstance(inp, ourlang.ConstantBytes):
        return repr(inp.value)

    if isinstance(inp, ourlang.ConstantTuple):
        return '(' + ', '.join(
            expression(x)
            for x in inp.value
        ) + ', )'

    if isinstance(inp, ourlang.ConstantStruct):
        return inp.struct_type3.name + '(' + ', '.join(
            expression(x)
            for x in inp.value
        ) + ')'

    if isinstance(inp, ourlang.VariableReference):
        return str(inp.variable.name)

    if isinstance(inp, ourlang.BinaryOp):
        return f'{expression(inp.left)} {inp.operator.name} {expression(inp.right)}'

    if isinstance(inp, ourlang.FunctionCall):
        args = ', '.join(
            expression(arg)
            for arg in inp.arguments
        )

        if isinstance(inp.function, ourlang.StructConstructor):
            return f'{inp.function.struct_type3.name}({args})'

        return f'{inp.function.name}({args})'

    if isinstance(inp, ourlang.FunctionReference):
        return str(inp.function.name)

    if isinstance(inp, ourlang.TupleInstantiation):
        args = ', '.join(
            expression(arg)
            for arg in inp.elements
        )

        return f'({args}, )'

    if isinstance(inp, ourlang.Subscript):
        varref = expression(inp.varref)
        index = expression(inp.index)

        return f'{varref}[{index}]'

    if isinstance(inp, ourlang.AccessStructMember):
        return f'{expression(inp.varref)}.{inp.member}'

    raise NotImplementedError(expression, inp)

def statement(inp: ourlang.Statement) -> Statements:
    """
    Render: A list of Phasm statements
    """
    if isinstance(inp, ourlang.StatementPass):
        yield 'pass'
        return

    if isinstance(inp, ourlang.StatementReturn):
        yield f'return {expression(inp.value)}'
        return

    if isinstance(inp, ourlang.StatementIf):
        yield f'if {expression(inp.test)}:'

        for stmt in inp.statements:
            for line in statement(stmt):
                yield f'    {line}' if line else ''

        yield ''
        return

    raise NotImplementedError(statement, inp)

def function(mod: ourlang.Module[Any], inp: ourlang.Function) -> str:
    """
    Render: Function body

    Imported functions only have "pass" as a body. Later on we might replace
    this by the function documentation, if any.
    """
    result = ''
    if inp.exported:
        result += '@exported\n'
    if inp.imported:
        result += '@imported\n'

    args = ', '.join(
        f'{p.name}: {type5(mod, p.type5)}'
        for p in inp.posonlyargs
    )

    result += f'def {inp.name}({args}) -> {type3(inp.returns_type3)}:\n'

    if inp.imported:
        result += '    pass\n'
    else:
        for stmt in inp.statements:
            for line in statement(stmt):
                result += f'    {line}\n' if line else '\n'

    return result


def module(inp: ourlang.Module[Any]) -> str:
    """
    Render: Module
    """
    result = ''

    for struct in inp.struct_definitions.values():
        if result:
            result += '\n'
        result += struct_definition(struct)

    for cdef in inp.constant_defs.values():
        if result:
            result += '\n'
        result += constant_definition(cdef)

    for func in inp.functions.values():
        if isinstance(func, ourlang.StructConstructor):
            # Auto generated
            continue

        if result:
            result += '\n'
        result += function(inp, func)

    return result