"""
Transformation logic for context caching. 

Why separate file? Make it easy to see how transformation works
"""

from typing import List, Tuple

from litellm.types.llms.openai import AllMessageValues
from litellm.types.llms.vertex_ai import CachedContentRequestBody
from litellm.utils import is_cached_message

from ..common_utils import get_supports_system_message
from ..gemini.transformation import (
    _gemini_convert_messages_with_history,
    _transform_system_message,
)


def get_first_continuous_block_idx(
    filtered_messages: List[Tuple[int, AllMessageValues]]  # (idx, message)
) -> int:
    """
    Find the array index that ends the first continuous sequence of message blocks.

    Args:
        filtered_messages: List of tuples containing (index, message) pairs

    Returns:
        int: The array index where the first continuous sequence ends
    """
    if not filtered_messages:
        return -1

    if len(filtered_messages) == 1:
        return 0

    current_value = filtered_messages[0][0]

    # Search forward through the array indices
    for i in range(1, len(filtered_messages)):
        if filtered_messages[i][0] != current_value + 1:
            return i - 1
        current_value = filtered_messages[i][0]

    # If we made it through the whole list, return the last index
    return len(filtered_messages) - 1


def separate_cached_messages(
    messages: List[AllMessageValues],
) -> Tuple[List[AllMessageValues], List[AllMessageValues]]:
    """
    Returns separated cached and non-cached messages.

    Args:
        messages: List of messages to be separated.

    Returns:
        Tuple containing:
        - cached_messages: List of cached messages.
        - non_cached_messages: List of non-cached messages.
    """
    cached_messages: List[AllMessageValues] = []
    non_cached_messages: List[AllMessageValues] = []

    # Extract cached messages and their indices
    filtered_messages: List[Tuple[int, AllMessageValues]] = []
    for idx, message in enumerate(messages):
        if is_cached_message(message=message):
            filtered_messages.append((idx, message))

    # Validate only one block of continuous cached messages
    last_continuous_block_idx = get_first_continuous_block_idx(filtered_messages)
    # Separate messages based on the block of cached messages
    if filtered_messages and last_continuous_block_idx is not None:
        first_cached_idx = filtered_messages[0][0]
        last_cached_idx = filtered_messages[last_continuous_block_idx][0]

        cached_messages = messages[first_cached_idx : last_cached_idx + 1]
        non_cached_messages = (
            messages[:first_cached_idx] + messages[last_cached_idx + 1 :]
        )
    else:
        non_cached_messages = messages

    return cached_messages, non_cached_messages


def transform_openai_messages_to_gemini_context_caching(
    model: str, messages: List[AllMessageValues], cache_key: str
) -> CachedContentRequestBody:
    supports_system_message = get_supports_system_message(
        model=model, custom_llm_provider="gemini"
    )

    transformed_system_messages, new_messages = _transform_system_message(
        supports_system_message=supports_system_message, messages=messages
    )

    transformed_messages = _gemini_convert_messages_with_history(messages=new_messages)
    data = CachedContentRequestBody(
        contents=transformed_messages,
        model="models/{}".format(model),
        displayName=cache_key,
    )
    if transformed_system_messages is not None:
        data["system_instruction"] = transformed_system_messages

    return data