//! [`AppError`] — the single error type returned by every use case.
//!
//! Per-port errors from the domain ([`domain::ports::FsError`],
//! [`domain::ports::StoreError`], …) are mapped into this application-level
//! error so that the presentation layer (Tauri commands) only ever has to deal
//! with one error shape when building its `ErrorDTO`.

use domain::ports::{
    AgentSessionError, EmbedderError, FsError, GitError, MemoryError, ProcessError, PtyError,
    RemoteError, RuntimeError, StoreError,
};
use domain::{AgentId, NodeId};

/// Errors surfaced by application use cases.
///
/// Each variant carries a stable, machine-readable `code` (see [`AppError::code`])
/// so the presentation layer can map it to an `ErrorDTO` without string matching.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
pub enum AppError {
    /// A requested resource was not found.
    #[error("not found: {0}")]
    NotFound(String),

    /// The input failed a domain/application invariant.
    #[error("invalid input: {0}")]
    Invalid(String),

    /// A filesystem operation failed.
    #[error("filesystem error: {0}")]
    FileSystem(String),

    /// A persistence (store) operation failed.
    #[error("store error: {0}")]
    Store(String),

    /// A process/PTY/runtime operation failed.
    #[error("process error: {0}")]
    Process(String),

    /// A git operation failed.
    #[error("git error: {0}")]
    Git(String),

    /// A remote (SSH/WSL) operation failed.
    #[error("remote error: {0}")]
    Remote(String),

    /// An agent is already running in a live cell and cannot be launched again
    /// (the "one live session per agent" invariant). Reuse goes through
    /// templates (instantiate → distinct agents); IdeA never multi-instances a
    /// single agent.
    #[error("agent {agent_id} is already running in cell {node_id}")]
    AgentAlreadyRunning {
        /// The agent that is already live.
        agent_id: AgentId,
        /// The layout cell (leaf) currently hosting that agent's live session.
        node_id: NodeId,
    },

    /// An unexpected internal error.
    #[error("internal error: {0}")]
    Internal(String),
}

impl AppError {
    /// A stable, machine-readable code for this error, intended for the
    /// `ErrorDTO` so the frontend can branch without parsing messages.
    #[must_use]
    pub fn code(&self) -> &'static str {
        match self {
            Self::NotFound(_) => "NOT_FOUND",
            Self::Invalid(_) => "INVALID",
            Self::FileSystem(_) => "FILESYSTEM",
            Self::Store(_) => "STORE",
            Self::Process(_) => "PROCESS",
            Self::Git(_) => "GIT",
            Self::Remote(_) => "REMOTE",
            Self::AgentAlreadyRunning { .. } => "AGENT_ALREADY_RUNNING",
            Self::Internal(_) => "INTERNAL",
        }
    }
}

impl From<FsError> for AppError {
    fn from(e: FsError) -> Self {
        match e {
            FsError::NotFound(p) => Self::NotFound(p),
            other => Self::FileSystem(other.to_string()),
        }
    }
}

impl From<StoreError> for AppError {
    fn from(e: StoreError) -> Self {
        match e {
            StoreError::NotFound => Self::NotFound("store item".to_owned()),
            other => Self::Store(other.to_string()),
        }
    }
}

impl From<MemoryError> for AppError {
    fn from(e: MemoryError) -> Self {
        match e {
            MemoryError::NotFound => Self::NotFound("memory note".to_owned()),
            MemoryError::Frontmatter(m) => Self::Invalid(m),
            other => Self::Store(other.to_string()),
        }
    }
}

impl From<EmbedderError> for AppError {
    /// Maps to [`AppError::Store`] — an embedder is a *derived* recall detail; its
    /// failure must degrade the recall (fallback to naïve), never fail hard. This
    /// mapping exists for completeness; recall adapters degrade *before* an
    /// embedder error ever reaches a use case.
    fn from(e: EmbedderError) -> Self {
        Self::Store(e.to_string())
    }
}

impl From<PtyError> for AppError {
    fn from(e: PtyError) -> Self {
        Self::Process(e.to_string())
    }
}

impl From<ProcessError> for AppError {
    fn from(e: ProcessError) -> Self {
        Self::Process(e.to_string())
    }
}

impl From<RuntimeError> for AppError {
    fn from(e: RuntimeError) -> Self {
        Self::Process(e.to_string())
    }
}

impl From<GitError> for AppError {
    fn from(e: GitError) -> Self {
        Self::Git(e.to_string())
    }
}

impl From<RemoteError> for AppError {
    fn from(e: RemoteError) -> Self {
        Self::Remote(e.to_string())
    }
}

impl From<AgentSessionError> for AppError {
    /// Maps a structured [`AgentSessionError`] (ARCHITECTURE §17.1) onto the single
    /// application error shape. `Start`/`Io`/`Decode`/`Timeout` are all execution
    /// failures of a live structured session (a process/SDK conversation), so they
    /// fold into [`AppError::Process`] — coherent with [`PtyError`]/[`ProcessError`],
    /// the byte-stream twins. The raw CLI JSON never travels through `Decode` (the
    /// adapter already redacted it), so this is safe to surface.
    fn from(e: AgentSessionError) -> Self {
        Self::Process(e.to_string())
    }
}