#!/usr/bin/env node
// Fly Strategic Group, LLC. Reference implementation of the frozen epb2 reader.
// BLAKE3 dependency: @noble/hashes (MIT), https://github.com/paulmillr/noble-hashes
import { blake3 } from '@noble/hashes/blake3.js';
import { createHash } from 'node:crypto';
import { readFile, stat, writeFile } from 'node:fs/promises';
import { pathToFileURL } from 'node:url';
const LENGTH=1312000, HALF=656000, ALPHABET='abcdefghijklmnopqrstuvwxyz ,.', DIGITS='0123456789abcdefghijklmnopqrs';
const utf8=s=>new TextEncoder().encode(s);
const concat=(...parts)=>{const out=new Uint8Array(parts.reduce((n,p)=>n+p.length,0));let offset=0;for(const p of parts){out.set(p,offset);offset+=p.length;}return out;};
const sha256=bytes=>createHash('sha256').update(bytes).digest('hex');
function stream(domain,message,count){
 const seed=blake3(concat(utf8(domain),Uint8Array.of(0),message)),out=new Uint8Array(count);let index=0,low=0,high=0;
 while(index<count){const counter=new Uint8Array(8),view=new DataView(counter.buffer);view.setUint32(0,low,true);view.setUint32(4,high,true);const block=blake3(concat(seed,counter),{dkLen:65536});
  for(const byte of block){if(byte<232)out[index++]=byte%29;if(index===count)break;}
  low=(low+1)>>>0;if(low===0)high=(high+1)>>>0;if(low===0&&high===0&&index<count)throw Error('Stream exhausted');
 }return out;
}
function transform(input,inverse){
 if(input.length!==LENGTH||input.some(d=>d>=29))throw Error('Invalid volume digits');
 let left=input.slice(0,HALF),right=input.slice(HALF);
 for(let step=0;step<8;step++){const round=inverse?7-step:step,f=stream(`EPB/v2/feistel/${round}`,inverse?left:right,HALF),next=new Uint8Array(HALF);
  for(let i=0;i<HALF;i++)next[i]=inverse?(right[i]-f[i]+29)%29:(left[i]+f[i])%29;
  if(inverse){right=left;left=next;}else{left=right;right=next;}
 }return concat(left,right);
}
export function reconstructAddress(address){
 if(typeof address!=='string'||Buffer.byteLength(address)>1400000)throw Error('Address exceeds limit');
 const match=/^epb2\/(0|[1-9a-s][0-9a-s]*)\/w([0-3])\/s([0-4])\/v([0-9]|[12][0-9]|3[01])(?:\/p([1-9][0-9]{0,2}))?$/.exec(address);
 if(!match||match[1].length>LENGTH||(match[5]&&Number(match[5])>410))throw Error('Invalid canonical epb2 address');
 const location=new Uint8Array(LENGTH);let carry=Number(match[2])*160+Number(match[3])*32+Number(match[4]);
 for(let i=LENGTH-1,j=match[1].length-1;i>=0;i--,j--){const value=(j>=0?DIGITS.indexOf(match[1][j]):0)*640+carry;location[i]=value%29;carry=Math.floor(value/29);}
 if(carry)throw Error('Address is outside the Library');
 const content=transform(location,true);
 for(let i=1;i<content.length;i++)if(content[i]===26&&content[i-1]===26)throw Error('Address is outside the valid reading Library');
 return {content,page:match[5]?Number(match[5]):null};
}
export function pageText(content,page){
 if(!Number.isInteger(page)||page<1||page>410||content.length!==LENGTH)throw Error('Page must be 1..410');
 const start=(page-1)*3200;let text='';for(let row=0;row<40;row++){for(let col=0;col<80;col++)text+=ALPHABET[content[start+row*80+col]];if(row<39)text+='\n';}return text;
}
// Fixture encoding is used only by --self-test, not by address reconstruction.
function fixtureAddress(location){
 const quotient=new Uint8Array(LENGTH);let remainder=0;
 for(let i=0;i<LENGTH;i++){const value=remainder*29+location[i];quotient[i]=Math.floor(value/640);remainder=value%640;}
 let first=0;while(first<quotient.length-1&&quotient[first]===0)first++;
 const chars=new Uint8Array(quotient.length-first);for(let i=0;i<chars.length;i++)chars[i]=DIGITS.charCodeAt(quotient[first+i]);
 return `epb2/${new TextDecoder().decode(chars)}/w${Math.floor(remainder/160)}/s${Math.floor((remainder%160)/32)}/v${remainder%32}/p173`;
}
export async function selfTest(){
 const vector=JSON.parse(await readFile(new URL('./golden-vectors.json',import.meta.url),'utf8'));
 const content=Uint8Array.from({length:LENGTH},(_,i)=>i%29);
 for(let i=0;i<vector.recipe.publicPhrase.length;i++)content[vector.recipe.offset+i]=ALPHABET.indexOf(vector.recipe.publicPhrase[i]);
 if(sha256(content)!==vector.volumeSha256)throw Error('Fixture volume mismatch');
 const location=transform(content,false);if(sha256(location)!==vector.locationSha256)throw Error('Fixture location mismatch');
 const address=fixtureAddress(location);if(sha256(utf8(address))!==vector.addressSha256)throw Error('Fixture address mismatch');
 const restored=reconstructAddress(address);if(sha256(restored.content)!==vector.volumeSha256)throw Error('Reconstruction mismatch');
 for(const page of [1,173,410])if(sha256(utf8(pageText(restored.content,page)))!==vector.pageTextSha256[page])throw Error('Fixture page mismatch');
 return {algorithm:'epb2',selfTest:'passed',pages:[1,173,410],volumeSha256:vector.volumeSha256};
}
async function main(){
 if(process.argv.length===3&&process.argv[2]==='--self-test'){console.log(JSON.stringify(await selfTest()));return;}
 const args={};for(let i=2;i<process.argv.length;i+=2){const key=process.argv[i],value=process.argv[i+1];if(!['--address-file','--page','--output'].includes(key)||args[key]||!value)throw Error('Use --address-file FILE [--page 1..410] --output FILE');args[key]=value;}
 if(!args['--address-file']||!args['--output'])throw Error('Address and output files are required');
 const metadata=await stat(args['--address-file']);if(!metadata.isFile()||metadata.size>1400000)throw Error('Address file exceeds limit');
 const address=await readFile(args['--address-file'],'utf8');
 // A single file-ending newline is accepted; address contents otherwise canonical.
 const value=address.endsWith('\n')?address.slice(0,-1):address;
 const {content,page:addressPage}=reconstructAddress(value),requested=args['--page'];
 if(requested&&!/^(?:[1-9][0-9]{0,2})$/.test(requested))throw Error('Page must be 1..410');
 const page=requested?Number(requested):addressPage;if(!page)throw Error('Choose a page with --page');
 const text=pageText(content,page);await writeFile(args['--output'],text,{mode:0o600});console.log(JSON.stringify({algorithm:'epb2',page,rows:40,columns:80,pageTextSha256:sha256(utf8(text))}));
}
if(process.argv[1]&&import.meta.url===pathToFileURL(process.argv[1]).href)main().catch(()=>{console.error('Verification failed. Check the address, page, files and epb2 reference version.');process.exitCode=1;});