use thiserror::Error;

pub type Result<T> = std::result::Result<T, Error>;

#[derive(Debug, Error)]
pub enum Error {
    #[error("tool not found: {0}")]
    ToolNotFound(String),

    #[error("resource not found: {0}")]
    ResourceNotFound(String),

    /// An in-flight request was cancelled — by the client (`notifications/
    /// cancelled`) or by the app (a human took the buffer back). The `String`
    /// is the cancelled request id.
    #[error("request cancelled: {0}")]
    Cancelled(String),

    #[error("invalid arguments for tool `{tool}`: {message}")]
    InvalidArgs { tool: String, message: String },

    #[error("tool `{tool}` failed: {message}")]
    ToolFailed { tool: String, message: String },

    /// Registered refusal — the tool exists in the surface but is not offered.
    /// The `reason` is stable text the model can act on.
    #[error("tool `{tool}` is not offered: {reason}")]
    Refused { tool: String, reason: String },

    /// Write tool called without a grant for its capability. Includes a stable
    /// suffix so small models learn not to retry.
    #[error("tool `{tool}` requires capability `{capability}` which was not granted; do not retry")]
    CapabilityDenied { tool: String, capability: String },

    #[error("protocol error: {0}")]
    Protocol(String),

    #[error("transport error: {0}")]
    Transport(String),

    #[error(transparent)]
    Json(#[from] serde_json::Error),

    #[error(transparent)]
    Io(#[from] std::io::Error),

    #[cfg(feature = "ollama")]
    #[error(transparent)]
    Http(#[from] reqwest::Error),
}