"""Generate the cases for the tier 2 interpreter.
Reads the instruction definitions from bytecodes.c.
Writes the cases to executor_cases.c.h, which is #included in ceval.c.
"""

import argparse
import os.path
import sys

from analyzer import (
    Analysis,
    Instruction,
    Uop,
    Part,
    analyze_files,
    Skip,
    StackItem,
    analysis_error,
)
from generators_common import (
    DEFAULT_INPUT,
    ROOT,
    write_header,
    emit_tokens,
    emit_to,
    REPLACEMENT_FUNCTIONS,
)
from cwriter import CWriter
from typing import TextIO, Iterator
from lexer import Token
from stack import StackOffset, Stack, SizeMismatch

DEFAULT_OUTPUT = ROOT / "Python/executor_cases.c.h"


def declare_variables(uop: Uop, out: CWriter) -> None:
    variables = {"unused"}
    for var in reversed(uop.stack.inputs):
        if var.name not in variables:
            type = var.type if var.type else "PyObject *"
            variables.add(var.name)
            if var.condition:
                out.emit(f"{type}{var.name} = NULL;\n")
            else:
                out.emit(f"{type}{var.name};\n")
    for var in uop.stack.outputs:
        if var.name not in variables:
            variables.add(var.name)
            type = var.type if var.type else "PyObject *"
            if var.condition:
                out.emit(f"{type}{var.name} = NULL;\n")
            else:
                out.emit(f"{type}{var.name};\n")


def tier2_replace_error(
    out: CWriter,
    tkn: Token,
    tkn_iter: Iterator[Token],
    uop: Uop,
    stack: Stack,
    inst: Instruction | None,
) -> None:
    out.emit_at("if ", tkn)
    out.emit(next(tkn_iter))
    emit_to(out, tkn_iter, "COMMA")
    label = next(tkn_iter).text
    next(tkn_iter)  # RPAREN
    next(tkn_iter)  # Semi colon
    out.emit(") ")
    c_offset = stack.peek_offset.to_c()
    try:
        offset = -int(c_offset)
        close = ";\n"
    except ValueError:
        offset = None
        out.emit(f"{{ stack_pointer += {c_offset}; ")
        close = "; }\n"
    out.emit("goto ")
    if offset:
        out.emit(f"pop_{offset}_")
    out.emit(label + "_tier_two")
    out.emit(close)


def tier2_replace_deopt(
    out: CWriter,
    tkn: Token,
    tkn_iter: Iterator[Token],
    uop: Uop,
    unused: Stack,
    inst: Instruction | None,
) -> None:
    out.emit_at("if ", tkn)
    out.emit(next(tkn_iter))
    emit_to(out, tkn_iter, "RPAREN")
    next(tkn_iter)  # Semi colon
    out.emit(") goto deoptimize;\n")


TIER2_REPLACEMENT_FUNCTIONS = REPLACEMENT_FUNCTIONS.copy()
TIER2_REPLACEMENT_FUNCTIONS["ERROR_IF"] = tier2_replace_error
TIER2_REPLACEMENT_FUNCTIONS["DEOPT_IF"] = tier2_replace_deopt


def write_uop(uop: Uop, out: CWriter, stack: Stack) -> None:
    try:
        out.start_line()
        if uop.properties.oparg:
            out.emit("oparg = CURRENT_OPARG();\n")
        for var in reversed(uop.stack.inputs):
            out.emit(stack.pop(var))
        if not uop.properties.stores_sp:
            for i, var in enumerate(uop.stack.outputs):
                out.emit(stack.push(var))
        for cache in uop.caches:
            if cache.name != "unused":
                if cache.size == 4:
                    type = cast = "PyObject *"
                else:
                    type = f"uint{cache.size*16}_t "
                    cast = f"uint{cache.size*16}_t"
                out.emit(f"{type}{cache.name} = ({cast})CURRENT_OPERAND();\n")
        emit_tokens(out, uop, stack, None, TIER2_REPLACEMENT_FUNCTIONS)
        if uop.properties.stores_sp:
            for i, var in enumerate(uop.stack.outputs):
                out.emit(stack.push(var))
    except SizeMismatch as ex:
        raise analysis_error(ex.args[0], uop.body[0])


SKIPS = ("_EXTENDED_ARG",)


def generate_tier2(
    filenames: list[str], analysis: Analysis, outfile: TextIO, lines: bool
) -> None:
    write_header(__file__, filenames, outfile)
    outfile.write(
        """
#ifdef TIER_ONE
    #error "This file is for Tier 2 only"
#endif
#define TIER_TWO 2
"""
    )
    out = CWriter(outfile, 2, lines)
    out.emit("\n")
    for name, uop in analysis.uops.items():
        if uop.properties.tier_one_only:
            continue
        if uop.is_super():
            continue
        if not uop.is_viable():
            out.emit(f"/* {uop.name} is not a viable micro-op for tier 2 */\n\n")
            continue
        out.emit(f"case {uop.name}: {{\n")
        declare_variables(uop, out)
        stack = Stack()
        write_uop(uop, out, stack)
        out.start_line()
        if not uop.properties.always_exits:
            stack.flush(out)
            if uop.properties.ends_with_eval_breaker:
                out.emit("CHECK_EVAL_BREAKER();\n")
            out.emit("break;\n")
        out.start_line()
        out.emit("}")
        out.emit("\n\n")
    outfile.write("#undef TIER_TWO\n")


arg_parser = argparse.ArgumentParser(
    description="Generate the code for the tier 2 interpreter.",
    formatter_class=argparse.ArgumentDefaultsHelpFormatter,
)

arg_parser.add_argument(
    "-o", "--output", type=str, help="Generated code", default=DEFAULT_OUTPUT
)

arg_parser.add_argument(
    "-l", "--emit-line-directives", help="Emit #line directives", action="store_true"
)

arg_parser.add_argument(
    "input", nargs=argparse.REMAINDER, help="Instruction definition file(s)"
)

if __name__ == "__main__":
    args = arg_parser.parse_args()
    if len(args.input) == 0:
        args.input.append(DEFAULT_INPUT)
    data = analyze_files(args.input)
    with open(args.output, "w") as outfile:
        generate_tier2(args.input, data, outfile, args.emit_line_directives)