"""Configuration for conversation summarization."""

from typing import Literal

from pydantic import BaseModel, ConfigDict, Field

ContextSizeType = Literal["fraction", "tokens", "messages"]


class ContextSize(BaseModel):
    """Context size specification for trigger or keep parameters."""

    model_config = ConfigDict(frozen=True)

    type: ContextSizeType = Field(description="Type of context size specification")
    value: int | float = Field(description="Value for the context size specification")

    def to_tuple(self) -> tuple[ContextSizeType, int | float]:
        """Convert to tuple format expected by SummarizationMiddleware."""
        return (self.type, self.value)


class SummarizationConfig(BaseModel):
    """Configuration for automatic conversation summarization."""

    model_config = ConfigDict(frozen=True)

    enabled: bool = Field(
        default=False,
        description="Whether to enable automatic conversation summarization",
    )
    model_name: str | None = Field(
        default=None,
        description="Model name to use for summarization (None = use a lightweight model)",
    )
    trigger: ContextSize | list[ContextSize] | None = Field(
        default=None,
        description="One or more thresholds that trigger summarization. When any threshold is met, summarization runs. "
        "Examples: {'type': 'messages', 'value': 50} triggers at 50 messages, "
        "{'type': 'tokens', 'value': 4000} triggers at 4000 tokens, "
        "{'type': 'fraction', 'value': 0.8} triggers at 80% of model's max input tokens",
    )
    keep: ContextSize = Field(
        default_factory=lambda: ContextSize(type="messages", value=20),
        description="Context retention policy after summarization. Specifies how much history to preserve. "
        "Examples: {'type': 'messages', 'value': 20} keeps 20 messages, "
        "{'type': 'tokens', 'value': 3000} keeps 3000 tokens, "
        "{'type': 'fraction', 'value': 0.3} keeps 30% of model's max input tokens",
    )
    trim_tokens_to_summarize: int | None = Field(
        default=4000,
        description="Maximum tokens to keep when preparing messages for summarization. Pass null to skip trimming.",
    )
    summary_prompt: str | None = Field(
        default=None,
        description="Custom prompt template for generating summaries. If not provided, uses the default LangChain prompt.",
    )