import {colorCode,PulseEdges} from './test-signals.js';
import {pairedSummary} from './paired-signals.js';

// Browser adapter. Source/device timestamps are not supplied by these APIs;
// this clock map is only a processing-time estimate, never release evidence.
// https://www.w3.org/TR/webaudio/#dom-baseaudiocontext-currenttime
// https://wicg.github.io/video-rvfc/
export class PairedObserver {
    constructor(context,video) {
        this.context=context;this.video=video;this.audio=[];this.frames=[];
        this.edges=new PulseEdges();this.previous=null;this.overflow=0;this.clockInvalid=false;
        this.canvas=document.createElement('canvas');this.canvas.width=16;this.canvas.height=16;
        this.drawing=this.canvas.getContext('2d',{willReadFrequently:true});
        this.offset=null;
    }
    audioMessage(data) {
        if(!Array.isArray(data.signals)||data.signals.length>32){this.clockInvalid=true;return;}
        this.overflow=Math.max(this.overflow,data.overflow??0);
        const before=performance.now(),clock=this.context.currentTime*1000,after=performance.now();
        if(this.context.state!=='running'||after-before>5||!Number.isFinite(clock)){this.clockInvalid=true;return;}
        const offset=(before+after)/2-clock;
        if(this.offset!==null&&Math.abs(offset-this.offset)>25)this.clockInvalid=true;
        this.offset=offset;
        for(const event of data.signals) {
            if(this.audio.length>=256){this.overflow++;continue;}
            this.audio.push({code:event.code,startMs:event.startMs+offset,endMs:event.endMs+offset});
        }
    }
    frame(timeMs) {
        if(!this.drawing||!this.video.videoWidth||!this.video.videoHeight)return;
        let pixels;
        try {
            // Small transient centre sample. Clear both the canvas and pixel
            // array immediately: no retained image, recording or upload.
            const w=this.video.videoWidth,h=this.video.videoHeight;
            this.drawing.drawImage(this.video,w/4,h/4,w/2,h/2,0,0,16,16);
            pixels=this.drawing.getImageData(0,0,16,16).data;
            const code=colorCode(pixels);
            const previous=this.previous;this.previous=timeMs;
            if(previous===null||timeMs<=previous||timeMs-previous>250)return;
            const event=this.edges.observe(code,previous,timeMs);
            if(event){if(this.frames.length<256)this.frames.push(event);else this.overflow++;}
        } catch {this.clockInvalid=true;}
        finally {pixels?.fill(0);this.drawing.clearRect(0,0,16,16);}
    }
    summary() {
        const result=pairedSummary(this.audio,this.frames);
        if(this.clockInvalid||this.overflow)result.estimatedMedianSignedMs=null;
        return {...result,audioSignals:this.audio.length,videoSignals:this.frames.length,
            overflow:this.overflow,clockInvalid:this.clockInvalid,
            note:'Coded signal / browser processing-time estimate only; input-clock calibration and source age are unmeasured.'};
    }
}