use serde::{Deserialize, Serialize};
use serde_json::Value;
use uuid::Uuid;

/// One gateway event with its journal sequence number. The wire contract
/// with the frontend (`frontend/src/lib/gateway/events.ts` mirrors it).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RunEventEnvelope {
    pub seq: i64,
    #[serde(flatten)]
    pub event: RunEventBody,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum RunEventBody {
    RunStarted {
        run_id: Uuid,
    },
    TextDelta {
        delta: String,
    },
    StepStarted {
        step_seq: i32,
        tool: String,
        input: Value,
    },
    StepFinished {
        step_seq: i32,
        status: String,
        output: Value,
    },
    /// A gated action awaits human review (§15): carries the exact preview
    /// of what will execute, surfaced as the approval card (§10).
    ApprovalRequired {
        approval_id: Uuid,
        category: String,
        action_type: String,
        preview: Value,
    },
    /// The run is blocked until the pending approval is decided.
    RunSuspended {
        approval_id: Uuid,
    },
    RunCompleted {
        message_id: String,
    },
    Error {
        message: String,
    },
}

impl RunEventBody {
    /// Stable name stored in `run_events.event_type`.
    pub fn type_name(&self) -> &'static str {
        match self {
            RunEventBody::RunStarted { .. } => "run_started",
            RunEventBody::TextDelta { .. } => "text_delta",
            RunEventBody::StepStarted { .. } => "step_started",
            RunEventBody::StepFinished { .. } => "step_finished",
            RunEventBody::ApprovalRequired { .. } => "approval_required",
            RunEventBody::RunSuspended { .. } => "run_suspended",
            RunEventBody::RunCompleted { .. } => "run_completed",
            RunEventBody::Error { .. } => "error",
        }
    }
}