//! Message Types
//!
//! Message structure used in conversations with LLM.
//! Can be easily created using [`Message::user`] or [`Message::assistant`].

use serde::{Deserialize, Serialize};

/// Message role
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum Role {
    /// User
    User,
    /// Assistant
    Assistant,
}

/// Conversation message
///
/// # Examples
///
/// ```ignore
/// use llm_worker::Message;
///
/// // User message
/// let user_msg = Message::user("Hello!");
///
/// // Assistant message
/// let assistant_msg = Message::assistant("Hi there!");
/// ```
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Message {
    /// Role
    pub role: Role,
    /// Content
    pub content: MessageContent,
}

/// Message content
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum MessageContent {
    /// Text content
    Text(String),
    /// Tool result
    ToolResult {
        tool_use_id: String,
        content: String,
    },
    /// Composite content (text + tool use, etc.)
    Parts(Vec<ContentPart>),
}

/// Content part
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type")]
pub enum ContentPart {
    /// Text
    #[serde(rename = "text")]
    Text { text: String },
    /// Tool use
    #[serde(rename = "tool_use")]
    ToolUse {
        id: String,
        name: String,
        input: serde_json::Value,
    },
    /// Tool result
    #[serde(rename = "tool_result")]
    ToolResult {
        tool_use_id: String,
        content: String,
    },
}

impl Message {
    /// Create a user message
    ///
    /// # Examples
    ///
    /// ```ignore
    /// use llm_worker::Message;
    /// let msg = Message::user("Hello");
    /// ```
    pub fn user(content: impl Into<String>) -> Self {
        Self {
            role: Role::User,
            content: MessageContent::Text(content.into()),
        }
    }

    /// Create an assistant message
    ///
    /// Usually auto-generated inside Worker,
    /// but can be manually created for history initialization, etc.
    pub fn assistant(content: impl Into<String>) -> Self {
        Self {
            role: Role::Assistant,
            content: MessageContent::Text(content.into()),
        }
    }

    /// Create a tool result message
    ///
    /// Auto-generated inside Worker after tool execution.
    /// Usually no need to create manually.
    pub fn tool_result(tool_use_id: impl Into<String>, content: impl Into<String>) -> Self {
        Self {
            role: Role::User,
            content: MessageContent::ToolResult {
                tool_use_id: tool_use_id.into(),
                content: content.into(),
            },
        }
    }
}