use serde::{Deserialize, Serialize};

/// The role of a participant in a chat conversation.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum ChatRole {
    /// Message sent by the human user
    User,
    /// Message generated by the AI assistant
    Assistant,
    /// System-level instruction (not displayed in UI)
    System,
}

/// The type of file attached to a chat message.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum AttachmentKind {
    /// Image file (png, jpg, webp, etc.)
    Image,
    /// Document file (pdf, docx, txt, etc.)
    Document,
    /// Source code file
    Code,
}

/// A file attachment on a chat message.
///
/// # Fields
///
/// * `name` - Original filename
/// * `kind` - Type of attachment for rendering
/// * `size_bytes` - File size in bytes
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct Attachment {
    pub name: String,
    pub kind: AttachmentKind,
    pub size_bytes: u64,
}

/// A single message in a chat conversation.
///
/// # Fields
///
/// * `id` - Unique message identifier
/// * `role` - Who sent this message
/// * `content` - The message text content
/// * `attachments` - Optional file attachments
/// * `timestamp` - ISO 8601 timestamp string
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct ChatMessage {
    pub id: String,
    pub role: ChatRole,
    pub content: String,
    pub attachments: Vec<Attachment>,
    pub timestamp: String,
}

/// A chat session containing a conversation history.
///
/// # Fields
///
/// * `id` - Unique session identifier
/// * `title` - Display title (usually derived from first message)
/// * `messages` - Ordered list of messages in the session
/// * `created_at` - ISO 8601 creation timestamp
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct ChatSession {
    pub id: String,
    pub title: String,
    pub messages: Vec<ChatMessage>,
    pub created_at: String,
}