// SPDX-License-Identifier: GPL-3.0-or-later
const copyBuffer=(buffer,rate=buffer.sampleRate)=>{
  const channels=Array.from({length:buffer.numberOfChannels},(_,i)=>new Float32Array(buffer.getChannelData(i)));
  return {sampleRate:rate,numberOfChannels:channels.length,length:channels[0]?.length||0,getChannelData:i=>channels[i]};
};
export async function decodeIR(context,bytes) {
  const decoded=await context.decodeAudioData(bytes.slice(0));
  return resampleIR(decoded,context.sampleRate);
}
export function resampleIR(buffer,targetRate) {
  if(!Number.isFinite(targetRate)||targetRate<8000||targetRate>96000||!buffer?.numberOfChannels||buffer.numberOfChannels>4||!buffer.length) throw new RangeError('Invalid IR or target sample rate');
  if(buffer.sampleRate===targetRate) return copyBuffer(buffer,targetRate);
  const length=Math.max(1,Math.round(buffer.length*targetRate/buffer.sampleRate));
  const channels=[];
  for(let ch=0;ch<buffer.numberOfChannels;ch++) {
    const input=buffer.getChannelData(ch), output=new Float32Array(length), ratio=buffer.sampleRate/targetRate;
    for(let i=0;i<length;i++) {const x=i*ratio, a=Math.min(Math.floor(x),input.length-1), b=Math.min(a+1,input.length-1), f=x-a;output[i]=input[a]*(1-f)+input[b]*f;}
    channels.push(output);
  }
  return {sampleRate:targetRate,numberOfChannels:channels.length,length,getChannelData:i=>channels[i]};
}
export function trimIR(buffer,{thresholdDb=-80}={}) {
  if(!Number.isFinite(thresholdDb)||thresholdDb>0||thresholdDb<-160) throw new RangeError('Invalid trim threshold');
  const channels=Array.from({length:buffer.numberOfChannels},(_,i)=>buffer.getChannelData(i));
  const threshold=10**(thresholdDb/20);let first=buffer.length,last=-1;
  for(let i=0;i<buffer.length;i++) {let peak=0;for(const channel of channels) peak=Math.max(peak,Math.abs(channel[i]));if(peak>=threshold){first=Math.min(first,i);last=i;}}
  if(last<0) first=last=0;
  const result=channels.map(channel=>channel.slice(first,last+1));
  return {buffer:{sampleRate:buffer.sampleRate,numberOfChannels:result.length,length:result[0]?.length||0,getChannelData:i=>result[i]},startFrame:first,endFrame:last+1};
}
export function normalizeIR(buffer,{peak=0.5}={}) {
  if(!Number.isFinite(peak)||peak<=0||peak>1) throw new RangeError('Peak must be in (0, 1]');
  const channels=Array.from({length:buffer.numberOfChannels},(_,i)=>new Float32Array(buffer.getChannelData(i)));
  let max=0;for(const channel of channels) for(const value of channel) max=Math.max(max,Math.abs(value));
  const gain=max===0?1:peak/max;for(const channel of channels) for(let i=0;i<channel.length;i++) channel[i]*=gain;
  return {sampleRate:buffer.sampleRate,numberOfChannels:channels.length,length:channels[0]?.length||0,getChannelData:i=>channels[i]};
}
export function prepareIR(context,buffer,{trim=false,normalize=true,peak=0.5,thresholdDb=-80}={}) {
  let result=resampleIR(buffer,context.sampleRate);
  if(trim) result=trimIR(result,{thresholdDb}).buffer;
  if(normalize) result=normalizeIR(result,{peak});
  return result;
}