const $ = document.querySelector.bind(document);
const $$ = (...args) => Array.prototype.slice.call(document.querySelectorAll(...args));

const isMac = /Macintosh/.test(window.navigator.userAgent);

function keyEventToShortcut(event) {
    let elideShift = event.key.toUpperCase() === event.key && event.shiftKey;
    return (event.ctrlKey ? 'Ctrl+' : '') +
        (event.altKey ? 'Alt+' : '') +
        (event.metaKey ? 'Meta+' : '') +
        (!elideShift && event.shiftKey ? 'Shift+' : '') +
        (event.key === ',' ? 'Comma' : event.key === ' ' ? 'Space' : event.key);
}

function prettifyShortcut(shortcut) {
    let keys = shortcut.split('+');

    if (isMac) {
        let cmdIdx = keys.indexOf('Meta');
        if (cmdIdx !== -1 && keys.length - cmdIdx > 2) {
            let tmp = keys[cmdIdx + 1];
            keys[cmdIdx + 1] = 'Meta';
            keys[cmdIdx] = tmp;
        }
    }

    let lastKey = keys[keys.length - 1];
    if (!keys.includes('Shift') && lastKey.toUpperCase() === lastKey && lastKey.toLowerCase() !== lastKey) {
        keys.splice(keys.length - 1, 0, 'Shift');
    }

    for (let i = 0; i < keys.length; i++) {
        if (isMac) {
            switch (keys[i]) {
                case 'Ctrl': keys[i] = '⌃'; break;
                case 'Alt': keys[i] = '⌥'; break;
                case 'Shift': keys[i] = '⇧'; break;
                case 'Meta': keys[i] = '⌘'; break;
            }
        }

        if (i === keys.length - 1 && i > 0 && keys[i].length === 1) {
            keys[i] = keys[i].toUpperCase();
        }

        switch (keys[i]) {
            case 'ArrowLeft': keys[i] = '←'; break;
            case 'ArrowRight': keys[i] = '→'; break;
            case 'ArrowUp': keys[i] = '↑'; break;
            case 'ArrowDown': keys[i] = '↓'; break;
            case 'Comma': keys[i] = ','; break;
            case 'Enter': keys[i] = '↩'; break;
            case ' ': keys[i] = 'Space'; break;
        }

        keys[i] = `<kbd>${keys[i]}</kbd>`;
    }

    return keys.join(isMac ? '' : ' + ');
}

function isTextField(element) {
    let name = element.nodeName.toLowerCase();
    return name === 'textarea' ||
        name === 'select' ||
        (name === 'input' && !['submit', 'reset', 'checkbox', 'radio'].includes(element.type)) ||
        element.isContentEditable;
}

let notTextField = event => !(event.target instanceof Node && isTextField(event.target));

let allShortcuts = [];
let shortcutsGroup = null;

class ShortcutHandler {
    constructor(element, override, filter = () => true) {
        this.element = element;
        this.map = {};
        this.active = this.map;
        this.override = override;
        this.filter = filter;
        this.timeout = null;

        this.handleKeyDown = this.handleKeyDown.bind(this);
        this.resetActive = this.resetActive.bind(this);
        this.addEventListeners();
    }

    addEventListeners() {
        this.element.addEventListener('keydown', this.handleKeyDown);
    }

    add(text, action, description = null, shownInHelp = true) {
        let shortcuts = text.trim().split(',').map(shortcut => shortcut.trim().split(' '));

        if (shortcutsGroup && shownInHelp) {
            shortcutsGroup.push({
                action,
                shortcut: text,
                description,
            })
        }

        for (let shortcut of shortcuts) {
            let node = this.map;
            for (let key of shortcut) {
                if (!node[key]) {
                    node[key] = {};
                }
                node = node[key];
                if (node.action) {
                    delete node.action;
                    delete node.shortcut;
                    delete node.description;
                }
            }

            node.action = action;
            node.shortcut = shortcut;
            node.description = description;
        }
    }

    group(...args) {
        if (typeof args[0] === 'string') this.fakeItem(args.shift());
        shortcutsGroup = [];

        args[0].bind(this)();

        if (shortcutsGroup && shortcutsGroup.length) allShortcuts.push(shortcutsGroup);
        shortcutsGroup = null;
    }

    bindElement(shortcut, element, ...other) {
        element = typeof element === 'string' ? $(element) : element;
        if (!element) return;
        this.add(shortcut, () => {
            if (isTextField(element)) {
                element.focus();
            } else {
                element.click();
            }
        }, ...other);
    }

    bindLink(shortcut, link, ...other) {
        this.add(shortcut, () => window.location.href = link, ...other);
    }

    bindCollection(prefix, elements, collectionDescription, itemDescription) {
        this.fakeItem(prefix + ' 1 – 9', collectionDescription);

        if (typeof elements === 'string') {
            elements = $$(elements);
        } else if (Array.isArray(elements)) {
            elements = elements.map(el => typeof el === 'string' ? $(el) : el);
        }

        for (let i = 1; i <= elements.length && i < 10; i++) {
            this.bindElement(`${prefix} ${i}`, elements[i - 1], `${itemDescription} #${i}`, false);
        }
    }

    fakeItem(shortcut, description = null) {
        let list = shortcutsGroup || allShortcuts;
        list.push({
            shortcut: description ? shortcut : null,
            description: description || shortcut,
        });
    }

    handleKeyDown(event) {
        if (event.defaultPrevented) return;
        if (['Control', 'Alt', 'Shift', 'Meta'].includes(event.key)) return;
        if (!this.filter(event)) return;

        let shortcut = keyEventToShortcut(event);

        if (!this.active[shortcut]) {
            this.resetActive();
            return;
        }

        this.active = this.active[shortcut];
        if (this.active.action) {
            event.stopPropagation();
            this.active.action(event);
            if (this.override) event.preventDefault();
            this.resetActive();
            return;
        }

        if (this.timeout) clearTimeout(this.timeout);
        this.timeout = window.setTimeout(this.resetActive, 1500);
    }

    resetActive() {
        this.active = this.map;
        if (this.timeout) {
            clearTimeout(this.timeout)
            this.timeout = null;
        }
    }
}

class ShortcutsHelpDialog {
    constructor() {
        let template = $('#dialog-template');
        let clonedTemplate = template.content.cloneNode(true);
        this.backdrop = clonedTemplate.children[0];
        this.dialog = clonedTemplate.children[1];

        this.dialog.classList.add('shortcuts-help');
        this.dialog.hidden = true;
        this.backdrop.hidden = true;

        document.body.appendChild(this.backdrop);
        document.body.appendChild(this.dialog);

        this.close = this.close.bind(this);

        this.dialog.querySelector('.dialog__title').textContent = 'List of shortcuts';
        this.dialog.querySelector('.dialog__close-button').addEventListener('click', this.close);
        this.backdrop.addEventListener('click', this.close);

        this.shortcuts = new ShortcutHandler(this.dialog, false);
        this.shortcuts.add('Escape', this.close, null, false);

        let shortcutsGroup;
        let shortcutsGroupTemplate = document.createElement('div');
        shortcutsGroupTemplate.className = 'shortcuts-group';

        for (let item of allShortcuts) {
            if (item.description && !item.shortcut) {
                shortcutsGroup = shortcutsGroupTemplate.cloneNode();
                this.dialog.querySelector('.dialog__content').appendChild(shortcutsGroup);

                let heading = document.createElement('h2');
                heading.className = 'shortcuts-group-heading';
                heading.textContent = item.description;
                shortcutsGroup.appendChild(heading);

            } else {
                let list = document.createElement('ul');
                list.className = 'shortcuts-list';

                for (let shortcut of item) {
                    let listItem = document.createElement('li');
                    listItem.className = 'shortcut-row';
                    list.appendChild(listItem);

                    let descriptionColumn = document.createElement('div')
                    descriptionColumn.className = 'shortcut-row__description';
                    descriptionColumn.textContent = shortcut.description;
                    listItem.appendChild(descriptionColumn);

                    let shortcutColumn = document.createElement('div');
                    shortcutColumn.className = 'shortcut-row__keys';
                    shortcutColumn.innerHTML = shortcut.shortcut.split(',')
                        .map(shortcuts => shortcuts.trim().split(' ').map(prettifyShortcut).join(' '))
                        .join(' <span class="kbd-or">or</span> ');
                    listItem.appendChild(shortcutColumn);
                }

                if (shortcutsGroup) {
                    shortcutsGroup.appendChild(list);
                }
            }
        }
    }

    open() {
        this.prevActiveElement = document.activeElement;

        document.body.overflow = 'hidden';
        this.backdrop.hidden = false;
        this.dialog.hidden = false;
        this.dialog.focus();
    }

    close() {
        document.body.overflow = '';
        this.backdrop.hidden = true;
        this.dialog.hidden = true;

        if (this.prevActiveElement) {
            this.prevActiveElement.focus();
            this.prevActiveElement = null;
        }
    }
}

window.addEventListener('load', () => {
    let helpDialog = null;
    let openHelp = () => {
        if (!helpDialog) helpDialog = new ShortcutsHelpDialog();
        helpDialog.open();
    };

    let onEditPage = typeof editTextarea !== 'undefined';

    // Global shortcuts work everywhere.
    let globalShortcuts = new ShortcutHandler(document, false);
    globalShortcuts.add(isMac ? 'Meta+/' : 'Ctrl+/', openHelp);

    // Page shortcuts work everywhere except on text fields.
    let pageShortcuts = new ShortcutHandler(document, false, notTextField);
    pageShortcuts.add('?', openHelp, null, false);

    // Common shortcuts
    pageShortcuts.group('Common', function () {
        this.bindCollection('g', '.top-bar__highlight-link', 'First 9 header links', 'Header link');
        this.bindLink('g h', '/', 'Home');
        this.bindLink('g l', '/list/', 'List of hyphae');
        this.bindLink('g r', '/recent-changes/', 'Recent changes');
        this.bindElement('g u', '.auth-links__user-link', 'Your profile′s hypha');
    });

    if (!onEditPage) {
        // Hypha shortcuts
        pageShortcuts.group('Hypha', function () {
            this.bindCollection('', 'article .wikilink', 'First 9 hypha′s links', 'Hypha link');
            this.bindElement('p, Alt+ArrowLeft, Ctrl+Alt+ArrowLeft', '.prevnext__prev', 'Next hypha');
            this.bindElement('n, Alt+ArrowRight, Ctrl+Alt+ArrowRight', '.prevnext__next', 'Previous hypha');
            this.bindElement('s, Alt+ArrowUp, Ctrl+Alt+ArrowUp', $$('.navi-title a').slice(1, -1).slice(-1)[0], 'Parent hypha');
            this.bindElement('c, Alt+ArrowDown, Ctrl+Alt+ArrowDown', '.subhyphae__link', 'First child hypha');

            this.bindElement('e, ' + (isMac ? "Meta+Enter" : "Ctrl+Enter"), '.btn__link_navititle[href^="/edit/"]', 'Edit this hypha');
            this.bindElement('v', '.hypha-info__link[href^="/hypha/"]', 'Go to hypha′s page');
            this.bindElement('a', '.hypha-info__link[href^="/media/"]', 'Go to media management');
            this.bindElement('h', '.hypha-info__link[href^="/history/"]', 'Go to history');
            this.bindElement('r', '.hypha-info__link[href^="/rename/"]', 'Rename this hypha');
            this.bindElement('b', '.hypha-info__link[href^="/backlinks/"]', 'Backlinks');
        });

    } else {
        // Hypha editor shortcuts. These work only on editor's text area.
        let editorShortcuts = new ShortcutHandler(editTextarea, true);

        let shortcuts = [
            // Win+Linux    Mac                  Action              Description
            ['Ctrl+b', 'Meta+b', wrapBold, 'Format: Bold'],
            ['Ctrl+i', 'Meta+i', wrapItalic, 'Format: Italic'],
            ['Ctrl+M', 'Meta+Shift+m', wrapMonospace, 'Format: Monospaced'],
            ['Ctrl+I', 'Meta+Shift+i', wrapHighlighted, 'Format: Highlight'],
            ['Ctrl+.', 'Meta+.', wrapLifted, 'Format: Superscript'],
            ['Ctrl+Comma', 'Meta+Comma', wrapLowered, 'Format: Subscript'],
            ['Ctrl+X', 'Meta+Shift+x', wrapStrikethrough, 'Format: Strikethrough'],
            ['Ctrl+k', 'Meta+k', wrapLink, 'Format: Inline link'],
            // Apparently, ⌘; conflicts with a Safari's hotkey. Whatever.
            ['Ctrl+;', 'Meta+;', insertDate, 'Insert date UTC'],
        ];

        editorShortcuts.group('Editor', function () {
            for (let shortcut of shortcuts) {
                if (isMac) {
                    this.add(shortcut[1], ...shortcut.slice(2))
                } else {
                    this.add(shortcut[0], ...shortcut.slice(2))
                }
            }
        });

        editorShortcuts.group(function () {
            this.bindElement(isMac ? 'Meta+Enter' : 'Ctrl+Enter', $('.edit-form__save'), 'Save changes');
        });
    }
});