// SPDX-License-Identifier: LGPL-3.0-or-later
// Read only the bounded Exif item, never search compressed image bytes for TIFF
// signatures. HEIF transforms take precedence to avoid applying rotation twice.
export function itemLocations(bytes,start,end){
 const bad=()=>Error('Unsupported HEIC orientation metadata. Convert it to JPG first.'),view=new DataView(bytes.buffer,bytes.byteOffset,bytes.byteLength);let position=start;
 function number(size){if(size>8||position+size>end)throw bad();let n=0;for(let i=0;i<size;i++)n=n*256+bytes[position++];if(!Number.isSafeInteger(n))throw bad();return n;}
 const version=number(1);if(version>2)throw bad();number(3);const sizes=number(1),other=number(1),offsetSize=sizes>>4,lengthSize=sizes&15,baseSize=other>>4,indexSize=version?other&15:0;
 const count=number(version<2?2:4);if(count>10000)throw bad();const items=new Map();
 for(let i=0;i<count;i++){
  const id=number(version<2?2:4),method=version?number(2)&15:0,reference=number(2),base=number(baseSize),n=number(2),extents=[];if(n>64)throw bad();
  for(let j=0;j<n;j++){if(indexSize)number(indexSize);extents.push({offset:number(offsetSize),length:number(lengthSize)});}
  if(items.has(id))throw bad();items.set(id,{method,reference,base,extents});
 }
 if(position!==end)throw bad();return items;
}
export function exifOrientation(bytes,items,locations,idat,hasTransform){
 if(hasTransform||!items.size)return 1;
 let orientation=1;
 for(const id of items){
  const location=locations.get(id);if(!location||location.reference||![0,1].includes(location.method))throw Error('Unsupported HEIC orientation metadata. Convert it to JPG first.');
  const total=location.extents.reduce((sum,e)=>sum+e.length,0);
  if(total<12||total>1024*1024)throw Error('Unsupported HEIC orientation metadata. Convert it to JPG first.');
  const payload=new Uint8Array(total);let position=0;
  for(const extent of location.extents){
   const start=location.base+extent.offset+(location.method===1?idat?.start||0:0),end=start+extent.length;
   if(!Number.isSafeInteger(start)||!Number.isSafeInteger(end)||start<0||end>bytes.length||location.method===1&&(!idat||start<idat.start||end>idat.end))throw Error('Unsupported HEIC orientation metadata. Convert it to JPG first.');
   payload.set(bytes.subarray(start,end),position);position+=extent.length;
  }
  const value=tiffOrientation(payload);if(orientation!==1&&value!==orientation)throw Error('Unsupported HEIC orientation metadata. Convert it to JPG first.');orientation=value;
 }
 return orientation;
}
export function tiffOrientation(payload){
 const invalid=()=>Error('Unsupported HEIC orientation metadata. Convert it to JPG first.');
 if(payload.length<12)throw invalid();
 const view=new DataView(payload.buffer,payload.byteOffset,payload.byteLength),start=4+view.getUint32(0);
 if(start+8>payload.length)throw invalid();
 const marker=view.getUint16(start),little=marker===0x4949;if(!little&&marker!==0x4d4d||view.getUint16(start+2,little)!==42)throw invalid();
 const offset=start+view.getUint32(start+4,little);if(offset+2>payload.length)throw invalid();
 const count=view.getUint16(offset,little);if(count>4096||offset+2+12*count>payload.length)throw invalid();
 for(let i=0;i<count;i++){const p=offset+2+i*12;if(view.getUint16(p,little)!==0x112)continue;
  if(view.getUint16(p+2,little)!==3||view.getUint32(p+4,little)!==1)throw invalid();const value=view.getUint16(p+8,little);if(value<1||value>8)throw invalid();return value;
 }
 return 1;
}
export function orientRgba(data,width,height,orientation){
 if(orientation===1)return {data,width,height};
 if(!Number.isInteger(orientation)||orientation<1||orientation>8||data.length!==width*height*4)throw Error('Invalid image orientation.');
 const swapped=orientation>=5,w=swapped?height:width,h=swapped?width:height,output=new Uint8ClampedArray(data.length);
 for(let y=0;y<height;y++)for(let x=0;x<width;x++){
  let dx,dy;
  switch(orientation){case 2:dx=width-1-x;dy=y;break;case 3:dx=width-1-x;dy=height-1-y;break;case 4:dx=x;dy=height-1-y;break;case 5:dx=y;dy=x;break;case 6:dx=height-1-y;dy=x;break;case 7:dx=height-1-y;dy=width-1-x;break;case 8:dx=y;dy=width-1-x;break;}
  const src=(y*width+x)*4,dst=(dy*w+dx)*4;output.set(data.subarray(src,src+4),dst);
 }
 return {data:output,width:w,height:h};
}