//! This file contains interactions with web_sys.
use wasm_bindgen::JsCast;

use crate::dom_types;

/// Reduces DRY
/// todo can't find a suitable trait for this. Seems like set_autofocus is
/// implemented individually for each of these el types.
//fn autofocus_helper<E: JsCast>(el: E) {
//    match val {
//        "true" => {
//            el.set_autofocus(true);
//            set_special = true;
//        },
//        "false" => {
//            el.set_autofocus(false);
//            set_special = true;
//        },
//        _ => ()
//    }
//}

/// Add a shim to make check logic more natural than the DOM handles it.
fn set_attr_shim(el_ws: &web_sys::Element, name: &str, val: &str) {
    let mut set_special = false;

    if name == "checked" {
        let input_el = el_ws.dyn_ref::<web_sys::HtmlInputElement>();
        if let Some(el) = input_el {
            match val {
                "true" => {
                    el.set_checked(true);
                },
                "false" => {
                    el.set_checked(false);
                },
                _ => ()
            }
            set_special = true;
        }
    }
    // todo DRY! Massive dry between checked and auto, and in autofocus.
    // https://www.w3schools.com/tags/att_autofocus.asp
    //todo needs to work for other type sof input!
    else if name == "autofocus" {

        if let Some(input) = el_ws.dyn_ref::<web_sys::HtmlInputElement>() {
//            autofocus_helper(input)
            match val {
                "true" => {
                    input.set_autofocus(true);
                },
                "false" => {
                    input.set_autofocus(false);
                },
                _ => ()
            }
            set_special = true;
        }
        if let Some(input) = el_ws.dyn_ref::<web_sys::HtmlTextAreaElement>() {
//             autofocus_helper(input)
            match val {
                "true" => {
                    input.set_autofocus(true);
                },
                "false" => {
                    input.set_autofocus(false);
                },
                _ => ()
            }
            set_special = true;
        }
        if let Some(input) = el_ws.dyn_ref::<web_sys::HtmlSelectElement>() {
//             autofocus_helper(input)
            match val {
                "true" => {
                    input.set_autofocus(true);
                },
                "false" => {
                    input.set_autofocus(false);
                },
                _ => ()
            }
            set_special = true;
        }
        if let Some(input) = el_ws.dyn_ref::<web_sys::HtmlButtonElement>() {
//             autofocus_helper(input)
            match val {
                "true" => {
                    input.set_autofocus(true);
                },
                "false" => {
                    input.set_autofocus(false);
                },
                _ => ()
            }
            set_special = true;
        }
    }

    if !set_special {
        el_ws.set_attribute(name, val).expect("Problem setting an atrribute.");
    }
}

/// Create and return a web_sys Element from our virtual-dom El. The web_sys
/// Element is a close analog to JS/DOM elements.
/// web-sys reference: https://rustwasm.github.io/wasm-bindgen/api/web_sys/struct.Element.html
/// Mozilla reference: https://developer.mozilla.org/en-US/docs/Web/HTML/Element\
/// See also: https://rustwasm.github.io/wasm-bindgen/api/web_sys/struct.Node.html
pub fn make_websys_el<Ms: Clone>(el_vdom: &dom_types::El<Ms>, document: &web_sys::Document) -> web_sys::Element {
    // Create the DOM-analog element; it won't render until attached to something.
    let tag = el_vdom.tag.as_str();
    let el_ws = match el_vdom.namespace {
        Some(ref ns) => document.create_element_ns(Some(ns.as_str()), tag).expect("Problem creating web-sys El"),
        None => document.create_element(tag).expect("Problem creating web-sys El")
    };

    for (name, val) in &el_vdom.attrs.vals {
        set_attr_shim(&el_ws, name, val);
    }

    // Style is just an attribute in the actual Dom, but is handled specially in our vdom;
    // merge the different parts of style here.
    if el_vdom.style.vals.keys().len() > 0 {
        el_ws.set_attribute("style", &el_vdom.style.to_string()).expect("Problem setting style");
    }

    // We store text as Option<String>, but set_text_content uses Option<&str>.
    // A naive match Some(t) => Some(&t) does not work.
    // See https://stackoverflow.com/questions/31233938/converting-from-optionstring-to-optionstr
    let text = el_vdom.text.as_ref().map(String::as_ref);
    if el_vdom.raw_html {
        el_ws.set_inner_html(text.unwrap())
    } else {
        el_ws.set_text_content(text);
    }

    // Don't attach listeners here,
    el_ws
}

/// Attaches the element, and all children, recursively. Only run this when creating a fresh vdom node, since
/// it performs a rerender of the el and all children; eg a potentially-expensive op.
/// This is where rendering occurs.
pub fn attach_els<Ms: Clone>(el_vdom: &mut dom_types::El<Ms>, parent: &web_sys::Element) {
    // No parent means we're operating on the top-level element; append it to the main div.
    // This is how we call this function externally, ie not through recursion.

    // Don't render if we're dealing with a dummy element.
    // todo get this working. it pr
    // odues panics
//    if el_vdom.is_dummy() == true { return }

    let el_ws = el_vdom.el_ws.take().expect("Missing websys el");

    parent.append_child(&el_ws).unwrap();

    // Perform side-effects specified for mounting.
    if let Some(mount_actions) = &mut el_vdom.did_mount {
        mount_actions(&el_ws)
    }

    // todo: It seesm like if text is present along with children, it'll bbe
    // todo shown before them instead of after. Fix this.

    for child in &mut el_vdom.children {
        // Raise the active level once per recursion.
        attach_els(child, &el_ws)
    }

    // Replace the web_sys el... Indiana-Jones-style.
    el_vdom.el_ws.replace(el_ws);
}

/// Recursively remove all children.
pub fn _remove_children(el: &web_sys::Element) {
    while let Some(child) = el.last_child() {
        el.remove_child(&child).unwrap();
    }
}

/// Update the attributes, style, text, and events of an element. Does not
/// process children, and assumes the tag is the same. Assume we've identfied
/// the most-correct pairing between new and old.
pub fn patch_el_details<Ms: Clone>(old: &mut dom_types::El<Ms>, new: &mut dom_types::El<Ms>,
           old_el_ws: &web_sys::Element, document: &web_sys::Document) {
    // Perform side-effects specified for updating
    if let Some(update_actions) = &mut old.did_update {
        update_actions(old_el_ws)
    }

    if old.attrs != new.attrs {
        for (key, new_val) in &new.attrs.vals {
            match old.attrs.vals.get(key) {
                Some(old_val) => {
                    // The value's different
                    if old_val != new_val {
                        set_attr_shim(&old_el_ws, key, new_val);
                    }
                },
                None =>  set_attr_shim(&old_el_ws, key, new_val),
            }
        }
        // Remove attributes that aren't in the new vdom.
        for name in old.attrs.vals.keys() {
            if new.attrs.vals.get(name).is_none() {
                old_el_ws.remove_attribute(name).expect("Removing an attribute");
            }
        }
    }

    // Patch style.
    if old.style != new.style {
        // We can't patch each part of style; rewrite the whole attribute.
        old_el_ws.set_attribute("style", &new.style.to_string())
            .expect("Setting style");
    }

    // Patch text
    if old.text != new.text {
        // This is not as straightforward as it looks: There can be multiple text nodes
        // in the DOM, even though our API only allows for 1 per element. If we
        // naively run set_text_content(), all child nodes will be removed.
        // Text is stored in special Text nodes that don't have a direct-relation to
        // the vdom.

        let text = new.text.clone().unwrap_or_default();

        if new.raw_html {
            old_el_ws.set_inner_html(&text)
        } else {
            if old.text.is_none() {
                // There's no old node to find: Add it.
                let new_next_node = document.create_text_node(&text);
                old_el_ws.append_child(&new_next_node).unwrap();
            } else {
                // Iterating over a NodeList, unfortunately, is not as clean as you might expect.
                if old_el_ws.has_child_nodes() {
                    let children = old_el_ws.child_nodes();
                    for i in 0..children.length() {
                        let node = children.item(i).unwrap();
                        // We've found it; there will be not more than 1 text node.
                        if node.node_type() == 3 {
                            node.set_text_content(Some(&text));
                            break;
                        }
                    }
                } else {
                    let new_next_node = document.create_text_node(&text);
                    old_el_ws.append_child(&new_next_node).unwrap();
                }
            }
        }
    }
}

/// Convenience function used in event handling: Convert an event target
/// to an input element; eg so you can take its value.
pub fn to_input(target: &web_sys::EventTarget ) -> &web_sys::HtmlInputElement {
    target.dyn_ref::<web_sys::HtmlInputElement>().expect("Unable to cast as an input element")
}

/// See to_input
pub fn to_textarea(target: &web_sys::EventTarget) -> &web_sys::HtmlTextAreaElement {
    target.dyn_ref::<web_sys::HtmlTextAreaElement>().expect("Unable to cast as a textarea element")
}

/// See to_input
pub fn to_select(target: &web_sys::EventTarget) -> &web_sys::HtmlSelectElement {
    target.dyn_ref::<web_sys::HtmlSelectElement>().expect("Unable to cast as a select element")
}

/// See to_input
pub fn to_html_el(target: &web_sys::EventTarget) -> &web_sys::HtmlElement {
    target.dyn_ref::<web_sys::HtmlElement>().expect("Unable to cast as an HTML element")
}

/// Convert a web_sys::Event to a web_sys::KeyboardEvent. Useful for extracting
/// info like which key has been pressed, which is not available with normal Events.
pub fn to_kbevent(event: &web_sys::Event) -> &web_sys::KeyboardEvent {
    event.dyn_ref::<web_sys::KeyboardEvent>().expect("Unable to cast as a keyboard event")
}

/// See to_kbevent
pub fn to_mouse_event(event: &web_sys::Event) -> &web_sys::MouseEvent {
    event.dyn_ref::<web_sys::MouseEvent>().expect("Unable to cast as a mouse event")
}