/*  DokuWiki MoaiEditor Scroll_to.js file
    Version : 0.5b (2026-05-08)
    Author  : MoaiTools <info@moaitools.org>
    License : GPL 3 (http://www.gnu.org/licenses/gpl.html) */

/*  Scrolls the preview (keeping it synchronized with the editor).

*/
MoaiEditor.ScrollSync = class {

    constructor(outer) {
        
        // Variables
        this.disabled = false;      // synchronization can be disabled temporarily when other processes want to take control
    }
    // ──────────────────────────────────── 
    init() {
        this.scroller = new MoaiEditor.Scroller(this);
    }
    // ──────────────────────────────────── 
    get isEnabled() {
        if (this.disabled  ||  moaiEditor.buttons.autoscroll.mode == 'off'  ||  !moaiEditor.layoutReady)
            return false;
        return true;
    }
    // ──────────────────────────────────── 
    // This function is called whenever the user scrolls the editor side
    onScroll(event) {
    
        // Exit if disabled by the user, by other process, or if the editor is not ready
        if (!this.isEnabled)
            return;
            
        // Exit if the editor scroll has not changed (to avoid interfering right after another process has done scrolling)
        const scroll = moaiEditor.editor.current.scroll.top;
        const sameScroll = Math.abs(scroll - this.lastScroll) <= 2;
        if (sameScroll)
            return;
            
        // Synchronize the scroll of the preview 
        const target = this.calcScroll().right;
        if (target !== null) {
            this.scroller.target = target;
            this.scroller.engaged = true;
        }
        // Remember last scroll position
        this.lastScroll = scroll;
    }
    // ──────────────────────────────────── 
    calcScroll() {    
        
        // There should be at least one match
        var matches = moaiEditor.matches.matches;
        if (matches.length == 0)
            return null;
    
        // Get the editor side scroll position
        const leftScroll = moaiEditor.editor.current.scroll.top;
        
        // Get the preview container top position relative to the screen
        this.container = moaiEditor.preview.container;
        this.containerTop = this.container.getBoundingClientRect().top;
        
        // Get the scroll points above and below our current scroll position
        var p1, p2, match;
        for (var i = 0; i < matches.length; i++) {
            if (matches[i].scroll === null)
                continue;
            match = matches[i];
            if (match.scroll.top > leftScroll) {
                p1 = this.getPoint(i-1, 'bottom');
                p2 = this.getPoint(i, 'top');
                break;
            }
            if (match.scroll.bottom > leftScroll) {
                p1 = this.getPoint(i, 'top');
                p2 = this.getPoint(i, 'bottom');
                break;
            }
        }
        // Exit if no scroll points where found
        if (match === undefined) {
            return null;
        }
        
        
        // Build bottom scroll point if needed
        if (p1 === undefined) {
            p1 = this.getPoint(i-1, 'bottom');
            p2 = this.getPoint(i, 'top');
        }
        
        // Get the normalized scroll progress between both scrollpoints on the editor side
        const normalized = (leftScroll - p1.left) / (p2.left - p1.left);
        
        // Compute the corresponding scroll on the preview side
        const right = p1.right + normalized * (p2.right - p1.right);
        
        // Debug line
        const scroll = {p1:p1, p2:p2, right:right};
        this.debugLine(scroll);
        
        // Return
        return scroll;
    }
    // ──────────────────────────────────── 
    getPoint(i, side) {
        var type, left, right;
        var linenum = side.toUpperCase();
        // Build a TOP scrollpoint if needed
        if (i < 0) {
            type = 'TOP';
            left = 0;
            right = 0; 
        // Build a BOTTOM scrollpoint if needed
        } else if (i >= moaiEditor.matches.matches.length) {
            type = 'BOTTOM';
            left = moaiEditor.editor.current.scroll.max;
            right = this.container.scrollHeight;
        // Get the scrollpoint from the match
        } else {
            const match = moaiEditor.matches.matches[i];
            type  = match.type,
            left  = match.scroll[side],
            right = match.handle.getBoundingClientRect()[side] - this.containerTop + this.container.scrollTop;
            linenum = match.startline;
            if (side == 'bottom')
                linenum = match.endline;
        }
        // Pack and return
        return {linenum:linenum, type:type, left:left, right:right, side:side};
    }
    // ──────────────────────────────────── 
    debugLine(scroll) {
        // Exit if debugline is not enabled
        const line = document.querySelector("#moai__debug div:nth-child(2)");
        if (!line) return;
        
        // Debug line
        const p1 = scroll.p1;
        const p2 = scroll.p2;
        const txt1 = "<"+scroll.p1.type+"> "+p1.side+" L"+p1.linenum;
        const txt2 = "<"+scroll.p2.type+"> "+p2.side+" L"+p2.linenum;
        const text = txt1+" ⇔ "+txt2;
        line.textContent = text;
    }
}; // End Class

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// ▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆

MoaiEditor.Scroller = class {

    constructor(outer) {     
        this.outer = outer;
        this.i = 0;
        this.target = null;
        this._engaged = false;
        this.onFrame();
    }
    get engaged() {
        return this._engaged;
    }
    set engaged(boolean) {
        this._engaged = boolean;
        this.lastScroll = moaiEditor.preview.scroll.top;
    }
    onFrame() {
        requestAnimationFrame(this.onFrame.bind(this));        
        //this.i += 1; if (this.i % 3 !== 0) return;      // Test other framerates
        const dt = Date.now() - this.lastTime;
        this.lastTime = Date.now();
        if (!this.engaged  ||  !this.outer.isEnabled  ||  this.target === null)
            return;  
        // Disengage if the user scrolled the preview
        const scroll = moaiEditor.preview.scroll.top;
        const userScrolled = Math.abs(scroll - this.lastScroll) > 2;
        if (userScrolled) {
            this.engaged = false;
            return;
        }
        // Scroll the preview
        const distance = this.target - scroll;
        const increment = 1*distance*dt/160;
        moaiEditor.preview.scroll.top = scroll + increment;
        this.lastScroll = scroll + increment;
    }
}; // End Class