//! Thin, swappable bindings to the vendored CodeMirror 6 bundle.
//!
//! The bundle (`web/cm6.js`, built from `web/cm/wrapper.js`) installs a
//! `window.__dovenest_cm` global. This module is the *only* place that knows how
//! to talk to it, so swapping the editor later means re-implementing just
//! these functions.
//!
//! The bundle is a separate `<script>`, so it may be missing (a failed load,
//! a stale cache). Every binding is therefore `catch`: a missing global
//! surfaces as an `Err` instead of a wasm trap.

use wasm_bindgen::JsCast;
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
extern "C" {
    #[wasm_bindgen(js_namespace = __dovenest_cm, js_name = create, catch)]
    fn js_create(
        container: &web_sys::Element,
        value: &str,
        filename: &str,
        editable: bool,
        on_update: Option<&js_sys::Function>,
    ) -> Result<JsValue, JsValue>;

    #[wasm_bindgen(js_namespace = __dovenest_cm, catch)]
    pub fn destroy(view: &JsValue) -> Result<(), JsValue>;

    /// Replace the whole document (used when (re)loading a file).
    #[wasm_bindgen(js_namespace = __dovenest_cm, js_name = setValue, catch)]
    pub fn set_value(view: &JsValue, text: &str) -> Result<(), JsValue>;

    #[wasm_bindgen(js_namespace = __dovenest_cm, js_name = getValue, catch)]
    fn js_get_value(view: &JsValue) -> Result<JsValue, JsValue>;

    #[wasm_bindgen(js_namespace = __dovenest_cm, catch)]
    pub fn focus(view: &JsValue) -> Result<(), JsValue>;
}

/// Extract a human-readable message from a JS error value.
fn err_str(e: JsValue) -> String {
    e.dyn_into::<js_sys::Error>()
        .ok()
        .and_then(|e| e.message().as_string())
        .unwrap_or_else(|| "editor error".to_string())
}

/// Create an editor inside `container` and return its view handle. Destroy
/// it with [`destroy`] when the host goes away.
///
/// `on_update` is called whenever the document changes (used to track the
/// editor's dirty state). The caller must keep the backing `Closure` alive
/// for as long as the editor exists.
pub fn create(
    container: &web_sys::Element,
    value: &str,
    filename: &str,
    editable: bool,
    on_update: Option<&js_sys::Function>,
) -> Result<JsValue, String> {
    js_create(container, value, filename, editable, on_update).map_err(err_str)
}

/// Read the current document text (used by the editor's save path).
pub fn get_value(view: &JsValue) -> Option<String> {
    js_get_value(view).ok()?.as_string()
}