from __future__ import annotations

from typing import Any

from tiny_gdn.smoltalk_chat import (
    NO_THINK_PREFIX,
    THINK_CONTROL_PREFIX,
    kwargs_from_inference_request,
    materialize_smoltalk_messages,
    merge_kwargs_with_system_message,
    resolve_reasoning_mode,
)
from tiny_gdn.tools import prepare_inference_messages

THINK_START = "<think>"
THINK_END = "</think>"


def decode_chat_completion(tokenizer: Any, token_ids: list[int]) -> str:
    return tokenizer.decode(token_ids, skip_special_tokens=False)


def append_assistant_generation_prompt(
    tokenizer: Any,
    token_ids: list[int],
    *,
    enable_thinking: bool | None = None,
) -> None:
    im_start = tokenizer.token_to_id("<|im_start|>")
    if im_start is None:
        raise RuntimeError("Tokenizer is missing <|im_start|>")
    token_ids.append(im_start)
    token_ids.extend(
        tokenizer.encode("assistant\n", add_special_tokens=False).ids
    )
    if enable_thinking is True:
        token_ids.extend(
            tokenizer.encode(THINK_CONTROL_PREFIX, add_special_tokens=False).ids
        )
    elif enable_thinking is False:
        token_ids.extend(
            tokenizer.encode(NO_THINK_PREFIX, add_special_tokens=False).ids
        )


def encode_chatml_messages(
    tokenizer: Any,
    messages: list[dict[str, Any]],
    *,
    tools: Any | None = None,
    enable_thinking: bool | None = None,
    xml_tools: Any | None = None,
    python_tools: Any | None = None,
) -> list[int]:
    if enable_thinking is None:
        prepared = prepare_inference_messages(messages, tools=tools)
        assistant_thinking_control = None
    else:
        kwargs = kwargs_from_inference_request(
            enable_thinking=enable_thinking,
            xml_tools=xml_tools,
            python_tools=python_tools,
            tools=tools,
        )
        prepared = materialize_smoltalk_messages(messages, kwargs)
        _, resolved = merge_kwargs_with_system_message(messages, kwargs)
        assistant_thinking_control = (
            resolve_reasoning_mode(
                resolved.enable_thinking,
                resolved.custom_instructions,
            )
            == "/think"
        )
    required_tokens = {
        token: tokenizer.token_to_id(token)
        for token in (
            "<|begin_of_text|>",
            "<|im_start|>",
            "<|im_end|>",
        )
    }
    if any(token_id is None for token_id in required_tokens.values()):
        raise RuntimeError("Tokenizer is missing ChatML special tokens")
    bos_id = required_tokens["<|begin_of_text|>"]
    im_start_id = required_tokens["<|im_start|>"]
    im_end_id = required_tokens["<|im_end|>"]
    if bos_id is None or im_start_id is None or im_end_id is None:
        raise RuntimeError("Tokenizer ChatML IDs could not be resolved")

    token_ids = [bos_id]
    newline_ids = tokenizer.encode("\n", add_special_tokens=False).ids
    allowed_roles = {"system", "user", "assistant"}
    for message_index, message in enumerate(prepared):
        role = message["role"]
        content = message["content"]
        masked_prefix = message.get("masked_prefix", "")
        if role not in allowed_roles:
            raise ValueError(
                f"Unsupported chat role at index {message_index}: {role!r}"
            )
        if not isinstance(masked_prefix, str):
            raise ValueError(
                f"Masked prefix at index {message_index} must be a string"
            )
        if not content.strip():
            raise ValueError(
                f"Chat content at index {message_index} must be non-empty"
            )
        token_ids.append(im_start_id)
        token_ids.extend(
            tokenizer.encode(f"{role}\n", add_special_tokens=False).ids
        )
        if masked_prefix:
            token_ids.extend(
                tokenizer.encode(masked_prefix, add_special_tokens=False).ids
            )
        token_ids.extend(
            tokenizer.encode(content, add_special_tokens=False).ids
        )
        token_ids.append(im_end_id)
        token_ids.extend(newline_ids)
    if prepared[-1]["role"] != "user":
        raise ValueError("The final chat message must have role 'user'")
    append_assistant_generation_prompt(
        tokenizer,
        token_ids,
        enable_thinking=assistant_thinking_control,
    )
    return token_ids