//! Data-plane HTTP surface. Mounted by the `picloud` all-in-one binary
//! under `/api` (so the path becomes `/api/execute/:id`) and by the
//! future split `picloud-orchestrator` binary at its own root.

use std::collections::BTreeMap;
use std::sync::Arc;
use std::time::Duration;

use axum::{
    body::Bytes,
    extract::{Path, Request, State},
    http::{HeaderMap, HeaderName, HeaderValue, StatusCode},
    response::{IntoResponse, Response},
    routing::post,
    Json, Router,
};
use chrono::Utc;
use picloud_executor_core::{ExecError, ExecRequest, ExecResponse, InvocationType};
use picloud_shared::{
    ExecutionId, ExecutionLog, ExecutionLogSink, ExecutionStatus, RequestId, ScriptId,
};
use serde_json::Value as Json_;
use uuid::Uuid;

use crate::client::ExecutorClient;
use crate::resolver::{ResolverError, ScriptResolver};
use crate::routing::RouteTable;

/// State shared by data-plane handlers.
pub struct DataPlaneState<E, R> {
    pub executor: Arc<E>,
    pub resolver: Arc<R>,
    pub log_sink: Arc<dyn ExecutionLogSink>,
    /// Routing table for user-defined paths. Shared with the manager
    /// (admin router writes; this side reads).
    pub routes: Arc<RouteTable>,
}

impl<E, R> Clone for DataPlaneState<E, R> {
    fn clone(&self) -> Self {
        Self {
            executor: self.executor.clone(),
            resolver: self.resolver.clone(),
            log_sink: self.log_sink.clone(),
            routes: self.routes.clone(),
        }
    }
}

/// Build the data-plane router. Handles `POST /execute/:id` — the
/// always-available ID-based bypass.
pub fn data_plane_router<E, R>(state: DataPlaneState<E, R>) -> Router
where
    E: ExecutorClient + 'static,
    R: ScriptResolver + 'static,
{
    Router::new()
        .route("/execute/{id}", post(execute_by_id::<E, R>))
        .with_state(state)
}

/// Build a router that handles ALL paths via the user-defined routing
/// table. Intended to be merged into the picloud app router as a
/// fallback (after the system routes are mounted).
pub fn user_routes_router<E, R>(state: DataPlaneState<E, R>) -> Router
where
    E: ExecutorClient + 'static,
    R: ScriptResolver + 'static,
{
    Router::new()
        .fallback(user_route_handler::<E, R>)
        .with_state(state)
}

// ----------------------------------------------------------------------------
// Handlers
// ----------------------------------------------------------------------------

async fn execute_by_id<E, R>(
    State(state): State<DataPlaneState<E, R>>,
    Path(id): Path<ScriptId>,
    headers: HeaderMap,
    body: Bytes,
) -> Result<Response, ApiError>
where
    E: ExecutorClient + 'static,
    R: ScriptResolver + 'static,
{
    let script = state
        .resolver
        .resolve(id)
        .await?
        .ok_or(ApiError::NotFound(id))?;

    let mut req = build_exec_request(id, &script.name, &headers, &body)?;
    req.sandbox_overrides = script.sandbox;
    let request_id = req.request_id;
    let request_path = req.path.clone();
    let request_headers = req.headers.clone();
    let request_body = req.body.clone();

    let timeout = Duration::from_secs(u64::from(script.timeout_seconds));
    let started = Utc::now();
    let outcome = state.executor.execute(&script.source, req, timeout).await;
    let finished = Utc::now();

    // Build and dispatch the audit log regardless of outcome. We await
    // the sink — recording the trail is part of correctness for an
    // audit-visible platform — but a sink failure must not mask the
    // user-facing result, so we only log a warning if it fails.
    let log = build_execution_log(
        id,
        request_id,
        request_path,
        request_headers,
        request_body,
        &outcome,
        started,
        finished,
    );
    if let Err(e) = state.log_sink.record(log).await {
        tracing::warn!(error = %e, script_id = %id, "failed to persist execution log");
    }

    Ok(exec_response_to_http(outcome?))
}

async fn user_route_handler<E, R>(
    State(state): State<DataPlaneState<E, R>>,
    request: Request,
) -> Result<Response, ApiError>
where
    E: ExecutorClient + 'static,
    R: ScriptResolver + 'static,
{
    let method = request.method().as_str().to_string();
    let uri = request.uri().clone();
    let path = uri.path().to_string();
    let query_str = uri.query().unwrap_or("").to_string();
    let host = request
        .headers()
        .get("host")
        .and_then(|h| h.to_str().ok())
        .unwrap_or("")
        .to_string();
    let headers = request.headers().clone();

    let Some(matched) = state.routes.match_request(&host, &method, &path) else {
        return Ok((
            StatusCode::NOT_FOUND,
            Json(serde_json::json!({
                "error": format!("no route matches {method} {path}")
            })),
        )
            .into_response());
    };

    let script = state
        .resolver
        .resolve(matched.matched.script_id)
        .await?
        .ok_or(ApiError::NotFound(matched.matched.script_id))?;

    // Drain the body now that we know we'll execute. 10 MiB cap matches
    // the conservative default response/request size in the blueprint.
    let body_bytes = match axum::body::to_bytes(request.into_body(), 10 * 1024 * 1024).await {
        Ok(b) => b,
        Err(e) => return Err(ApiError::BadRequest(format!("body read failed: {e}"))),
    };

    let mut req = build_exec_request(
        matched.matched.script_id,
        &script.name,
        &headers,
        &body_bytes,
    )?;
    req.path = path;
    req.params = matched.params;
    req.query = parse_query_string(&query_str);
    req.rest = matched.rest.unwrap_or_default();
    req.sandbox_overrides = script.sandbox;

    let request_id = req.request_id;
    let request_path = req.path.clone();
    let request_headers = req.headers.clone();
    let request_body = req.body.clone();

    let timeout = Duration::from_secs(u64::from(script.timeout_seconds));
    let started = Utc::now();
    let outcome = state.executor.execute(&script.source, req, timeout).await;
    let finished = Utc::now();

    let log = build_execution_log(
        matched.matched.script_id,
        request_id,
        request_path,
        request_headers,
        request_body,
        &outcome,
        started,
        finished,
    );
    if let Err(e) = state.log_sink.record(log).await {
        tracing::warn!(
            error = %e,
            script_id = %matched.matched.script_id,
            "failed to persist execution log"
        );
    }

    Ok(exec_response_to_http(outcome?))
}

fn parse_query_string(s: &str) -> BTreeMap<String, String> {
    let mut out = BTreeMap::new();
    if s.is_empty() {
        return out;
    }
    for pair in s.split('&') {
        let (k, v) = match pair.split_once('=') {
            Some((k, v)) => (k, v),
            None => (pair, ""),
        };
        let key = urlencoding::decode(k)
            .map(std::borrow::Cow::into_owned)
            .unwrap_or_default();
        let val = urlencoding::decode(v)
            .map(std::borrow::Cow::into_owned)
            .unwrap_or_default();
        out.insert(key, val);
    }
    out
}

// ----------------------------------------------------------------------------
// Marshalling
// ----------------------------------------------------------------------------

fn build_exec_request(
    id: ScriptId,
    name: &str,
    headers: &HeaderMap,
    body: &Bytes,
) -> Result<ExecRequest, ApiError> {
    let mut hmap = BTreeMap::new();
    for (k, v) in headers {
        if let Ok(s) = v.to_str() {
            hmap.insert(k.as_str().to_string(), s.to_string());
        }
    }

    let body_json: Json_ = if body.is_empty() {
        Json_::Null
    } else {
        serde_json::from_slice(body)
            .map_err(|e| ApiError::BadRequest(format!("invalid JSON body: {e}")))?
    };

    Ok(ExecRequest {
        execution_id: ExecutionId::new(),
        request_id: RequestId::new(),
        script_id: id,
        script_name: name.to_string(),
        invocation_type: InvocationType::Http,
        path: format!("/api/execute/{id}"),
        headers: hmap,
        body: body_json,
        params: BTreeMap::new(),
        query: BTreeMap::new(),
        rest: String::new(),
        // Overwritten by the handler after the script is resolved.
        sandbox_overrides: picloud_shared::ScriptSandbox::default(),
    })
}

fn exec_response_to_http(resp: ExecResponse) -> Response {
    let status =
        StatusCode::from_u16(resp.status_code).unwrap_or(StatusCode::INTERNAL_SERVER_ERROR);

    let mut http_headers = HeaderMap::new();
    for (k, v) in resp.headers {
        if let (Ok(name), Ok(value)) = (k.parse::<HeaderName>(), v.parse::<HeaderValue>()) {
            http_headers.insert(name, value);
        }
    }
    http_headers
        .entry(axum::http::header::CONTENT_TYPE)
        .or_insert_with(|| HeaderValue::from_static("application/json"));

    (status, http_headers, Json(resp.body)).into_response()
}

#[allow(clippy::too_many_arguments)]
fn build_execution_log(
    script_id: ScriptId,
    request_id: RequestId,
    request_path: String,
    request_headers: BTreeMap<String, String>,
    request_body: Json_,
    outcome: &Result<ExecResponse, ExecError>,
    started: chrono::DateTime<Utc>,
    finished: chrono::DateTime<Utc>,
) -> ExecutionLog {
    let duration_ms = u64::try_from(
        finished
            .signed_duration_since(started)
            .num_milliseconds()
            .max(0),
    )
    .unwrap_or(0);

    let (status, response_code, response_body, script_logs) = match outcome {
        Ok(resp) => {
            let logs = serde_json::to_value(&resp.logs).unwrap_or(Json_::Array(vec![]));
            (
                ExecutionStatus::Success,
                Some(resp.status_code),
                Some(resp.body.clone()),
                logs,
            )
        }
        Err(e) => {
            let status = match e {
                ExecError::Timeout(_) => ExecutionStatus::Timeout,
                ExecError::OperationBudgetExceeded => ExecutionStatus::BudgetExceeded,
                _ => ExecutionStatus::Error,
            };
            (
                status,
                None,
                Some(serde_json::json!({ "error": e.to_string() })),
                Json_::Array(vec![]),
            )
        }
    };

    ExecutionLog {
        id: Uuid::new_v4(),
        script_id,
        request_id,
        request_path,
        request_headers,
        request_body,
        response_code,
        response_body,
        script_logs,
        duration_ms,
        status,
        created_at: started,
    }
}

// ----------------------------------------------------------------------------
// Errors
// ----------------------------------------------------------------------------

#[derive(Debug, thiserror::Error)]
pub enum ApiError {
    #[error("script not found: {0}")]
    NotFound(ScriptId),

    #[error("bad request: {0}")]
    BadRequest(String),

    #[error("resolver error: {0}")]
    Resolver(#[from] ResolverError),

    #[error("execution error: {0}")]
    Exec(#[from] ExecError),
}

impl IntoResponse for ApiError {
    fn into_response(self) -> Response {
        use ApiError as E;
        let (status, message) = match &self {
            E::NotFound(_) => (StatusCode::NOT_FOUND, self.to_string()),
            E::BadRequest(_) => (StatusCode::BAD_REQUEST, self.to_string()),
            E::Resolver(e) => {
                tracing::error!(error = %e, "resolver failure");
                (
                    StatusCode::INTERNAL_SERVER_ERROR,
                    "internal error".to_string(),
                )
            }
            E::Exec(e) => match e {
                ExecError::Parse(_) | ExecError::InvalidResponse(_) => {
                    (StatusCode::UNPROCESSABLE_ENTITY, e.to_string())
                }
                ExecError::Timeout(_) => (StatusCode::GATEWAY_TIMEOUT, e.to_string()),
                ExecError::OperationBudgetExceeded => {
                    (StatusCode::INSUFFICIENT_STORAGE, e.to_string())
                }
                ExecError::Runtime(_) => (StatusCode::BAD_GATEWAY, e.to_string()),
            },
        };
        (status, Json(serde_json::json!({ "error": message }))).into_response()
    }
}