import { createHash, createPublicKey, verify } from 'node:crypto';
import { z } from 'zod';
import { NETWORK, CONSENSUS, MAX_TARGET, headerMessage, blockClaimMessage, nftTransferMessage, nftTradeMessage, statsSnapshotTuple,
  type BlockHeader, type TestnetBlock, type NftTransfer, type NftState, type NftStateLayer,
  isNftTrade, type NftStateView, type NftTrade, type TestnetTransaction, type MiningTemplate } from '../../shared/testnet.ts';
import type { Article } from '../../shared/protocol.ts';
import { deriveStats, type MintStatsSnapshot } from '../../shared/enrichment.ts';
import type { PowEngine } from './randomx.ts';
import { NETWORK_GENESIS_TIME } from '../../shared/network.ts';

export const sha256 = (data: string | Uint8Array) => createHash('sha256').update(data).digest('hex');
export { MAX_TARGET };
// Consensus manifest: an independently running node derives exactly the same genesis.
export const GENESIS_TIME = NETWORK_GENESIS_TIME;
export const CHAIN_ID = sha256(JSON.stringify([NETWORK, CONSENSUS, GENESIS_TIME, MAX_TARGET]));
export const GENESIS_HASH = sha256(`${NETWORK}:genesis:${CHAIN_ID}`);
export const INITIAL_KEY = sha256(`${NETWORK}:initial-key:${CHAIN_ID}`);
const hex = z.string().regex(/^[a-f0-9]{64}$/);
const key = z.string().regex(/^[A-Za-z0-9+/]+={0,2}$/).max(256);
const signature = z.string().regex(/^[A-Za-z0-9+/]+={0,2}$/).length(88);
const integer = z.number().int().min(0).max(Number.MAX_SAFE_INTEGER);
export const transferSchema = z.object({ network: z.literal(NETWORK), chainId: z.literal(CHAIN_ID),
  cardHash: hex, from: hex, to: hex, sequence: integer, publicKey: key, signature }).strict();
const tradeLegSchema = z.object({ cardHash: hex, sequence: integer }).strict();
export const tradeSchema = z.object({ type: z.literal('trade'), network: z.literal(NETWORK), chainId: z.literal(CHAIN_ID),
  proposer: hex, counterparty: hex, offered: z.array(tradeLegSchema).min(1).max(CONSENSUS.maxTradeCards),
  requested: z.array(tradeLegSchema).min(1).max(CONSENSUS.maxTradeCards),
  proposerPublicKey: key, proposerSignature: signature, counterpartyPublicKey: key,
  counterpartySignature: signature }).strict().superRefine((trade, ctx) => {
    const offered = new Set(trade.offered.map(leg => leg.cardHash));
    const requested = new Set(trade.requested.map(leg => leg.cardHash));
    if (trade.proposer === trade.counterparty) ctx.addIssue({ code: 'custom', message: 'Trade parties must differ' });
    if (offered.size !== trade.offered.length || requested.size !== trade.requested.length ||
        trade.requested.some(leg => offered.has(leg.cardHash))) {
      ctx.addIssue({ code: 'custom', message: 'Trade cards must be unique and cannot appear on both sides' });
    }
    if (!verifySignature(trade.proposerPublicKey, trade.proposer, nftTradeMessage(trade), trade.proposerSignature) ||
        !verifySignature(trade.counterpartyPublicKey, trade.counterparty, nftTradeMessage(trade), trade.counterpartySignature)) {
      ctx.addIssue({ code: 'custom', message: 'Trade requires valid signatures from both parties' });
    }
  });
export const transactionSchema = z.union([transferSchema, tradeSchema]);
const articleSchema = z.object({ pageId: integer.positive(), title: z.string().trim().min(1).max(200),
  extract: z.string().trim().min(1).max(1000), image: z.string().url().max(1500),
  url: z.string().url().max(500), revisionId: integer.positive(),
  source: z.literal('live'), category: z.string().trim().min(1).max(50) }).strict().superRefine((article, ctx) => {
    if (article.url !== `https://en.wikipedia.org/?curid=${article.pageId}`) {
      ctx.addIssue({ code: 'custom', message: 'Article URL must identify its English Wikipedia page', path: ['url'] });
    }
    try {
      const image = new URL(article.image);
      if (image.protocol !== 'https:' || !['https://upload.wikimedia.org', 'https://thumb.wikimedia.org'].includes(image.origin) ||
          image.username || image.password || image.hash) {
        ctx.addIssue({ code: 'custom', message: 'Article image must use a Wikimedia HTTPS host', path: ['image'] });
      }
    } catch { ctx.addIssue({ code: 'custom', message: 'Invalid article image URL', path: ['image'] }); }
  });
const monthSchema = z.string().regex(/^\d{4}-(0[1-9]|1[0-2])$/);
const statsSnapshotSchema = z.object({ capturedAt: z.string().datetime(), revisionId: integer.positive(),
  pageBytes: integer, languageCount: integer, languagesTruncated: z.boolean(),
  pageviews: z.object({ status: z.enum(['available', 'unavailable']),
    months: z.array(z.object({ month: monthSchema, views: integer }).strict()).max(6),
    latestMonth: monthSchema, total: integer.nullable(), dailyAverage: z.number().min(0).nullable(),
    trendPercent: z.number().finite().nullable() }).strict(),
  stats: z.object({ attention: z.number().int().min(0).max(100).nullable(),
    depth: z.number().int().min(0).max(100), reach: z.number().int().min(0).max(100) }).strict() }).strict()
  .superRefine((snapshot, ctx) => {
    const views = snapshot.pageviews;
    if (views.status === 'available') {
      if (views.months.length !== 6 || views.months[5]?.month !== views.latestMonth) {
        ctx.addIssue({ code: 'custom', message: 'Available pageviews require six months ending at latestMonth', path: ['pageviews', 'months'] });
      } else {
        const total = views.months.reduce((sum, item) => sum + item.views, 0);
        const latest = views.months[5].views;
        const prior = views.months[4].views;
        const [year, month] = views.latestMonth.split('-').map(Number);
        const days = new Date(Date.UTC(year, month, 0)).getUTCDate();
        const trend = prior > 0 ? (latest - prior) / prior * 100 : null;
        if (!Number.isSafeInteger(total) || views.total !== total || views.dailyAverage !== latest / days ||
            views.trendPercent !== trend) {
          ctx.addIssue({ code: 'custom', message: 'Pageview summaries do not match the monthly values', path: ['pageviews'] });
        }
      }
    } else if (views.months.length !== 0 || views.total !== null || views.dailyAverage !== null || views.trendPercent !== null) {
      ctx.addIssue({ code: 'custom', message: 'Unavailable pageviews must not include invented counts', path: ['pageviews'] });
    }
    const monthlyViews = views.status === 'available' ? views.months[5]?.views ?? null : null;
    const expected = deriveStats(snapshot.pageBytes, snapshot.languageCount, monthlyViews);
    if (snapshot.stats.attention !== expected.attention || snapshot.stats.depth !== expected.depth ||
        snapshot.stats.reach !== expected.reach) {
      ctx.addIssue({ code: 'custom', message: 'Derived statistics do not match the page metrics', path: ['stats'] });
    }
  });
export const blockSchema = z.object({ version: z.literal(6), network: z.literal(NETWORK), chainId: z.literal(CHAIN_ID),
  height: integer, previousHash: hex, createdAt: integer, article: articleSchema, statsSnapshot: statsSnapshotSchema, owner: hex,
  publicKey: key, nonce: integer, target: hex, key: hex, transactionsRoot: hex, stateRoot: hex,
  hash: hex, tokenId: hex, powHash: hex, signature, transactions: z.array(transactionSchema).max(CONSENSUS.maxTransactions) }).strict();

export function address(publicKey: string): string { return sha256(Buffer.from(publicKey, 'base64')); }
export function verifySignature(publicKey: string, owner: string, message: string, sig: string): boolean {
  try {
    const bytes = Buffer.from(publicKey, 'base64');
    if (bytes.toString('base64') !== publicKey || address(publicKey) !== owner) return false;
    const k = createPublicKey({ key: bytes, type: 'spki', format: 'der' });
    if (k.asymmetricKeyType !== 'ec' || k.asymmetricKeyDetails?.namedCurve !== 'prime256v1') return false;
    if (!k.export({ format: 'der', type: 'spki' }).equals(bytes)) return false;
    return verify('sha256', Buffer.from(message), { key: k, dsaEncoding: 'ieee-p1363' }, Buffer.from(sig, 'base64'));
  } catch { return false; }
}
export function transferId(t: NftTransfer): string {
  // Exclude malleable ECDSA signature bytes from transaction identity.
  return sha256(nftTransferMessage(t));
}
export function transactionId(transaction: TestnetTransaction): string {
  if (isNftTrade(transaction)) return sha256(nftTradeMessage(transaction));
  return transferId(transaction);
}
export function merkleRoot(leaves: string[]): string {
  if (!leaves.length) return sha256(`${NETWORK}:empty`);
  let layer = leaves.map(leaf => sha256(Buffer.concat([Buffer.from([0]), Buffer.from(leaf,'hex')])));
  while (layer.length > 1) {
    const next: string[] = [];
    for (let i = 0; i < layer.length; i += 2) next.push(sha256(Buffer.concat([Buffer.from([1]),
      Buffer.from(layer[i], 'hex'), Buffer.from(layer[i + 1] ?? layer[i], 'hex')])));
    layer = next;
  }
  // Commit the count as well: odd-leaf padding must not make [a,b,c] equal [a,b,c,c].
  return sha256(JSON.stringify([NETWORK,'merkle',leaves.length,layer[0]]));
}
export function materializeState(state: NftStateView): NftState {
  const layers: NftState[] = [];
  let cursor: NftStateView = state;
  while (isStateLayer(cursor)) {
    layers.push(cursor.changes);
    cursor = cursor.parent;
  }
  const result: NftState = Object.assign(Object.create(null) as NftState, cursor as NftState);
  for (let i = layers.length - 1; i >= 0; i--) Object.assign(result, layers[i]);
  return result;
}
function stateEntry(state: NftStateView, id: string): NftState[string] | undefined {
  let cursor: NftStateView = state;
  while (isStateLayer(cursor)) {
    if (Object.hasOwn(cursor.changes, id)) return cursor.changes[id];
    cursor = cursor.parent;
  }
  return (cursor as NftState)[id];
}
function isStateLayer(state: NftStateView): state is NftStateLayer {
  return (state as NftStateLayer).kind === 'layer';
}
export function stateRoot(state: NftStateView): string {
  const materialized = materializeState(state);
  return merkleRoot(Object.keys(materialized).sort().map(id => {
    const n = materialized[id]; return sha256(JSON.stringify([id, n.owner, n.sequence, n.mintedHeight, n.pageId]));
  }));
}
export function mintId(h: Pick<BlockHeader, 'previousHash' | 'height' | 'owner' | 'article' | 'statsSnapshot'>): string {
  return sha256(JSON.stringify([NETWORK, CHAIN_ID, 'mint', h.previousHash, h.height, h.owner,
    h.article.pageId, statsSnapshotTuple(h.statsSnapshot)]));
}
export function miningBlob(header: BlockHeader): Buffer {
  const nonce = Buffer.alloc(8);
  nonce.writeBigUInt64LE(BigInt(header.nonce));
  return Buffer.concat([Buffer.from(sha256(headerMessage(header)), 'hex'), nonce]);
}
export function workFor(target: string): bigint { return (1n << 256n) / (BigInt(`0x${target}`) + 1n); }
export function expectedKey(ancestors: TestnetBlock[], height: number): string {
  const keyHeight = Math.floor(Math.max(0, height - CONSENSUS.epochDelay) / CONSENSUS.epochBlocks) * CONSENSUS.epochBlocks;
  return keyHeight === 0 ? INITIAL_KEY : ancestors[keyHeight - 1].hash;
}
export function expectedTarget(ancestors: TestnetBlock[]): string {
  if (!ancestors.length) return MAX_TARGET;
  const parent = ancestors.at(-1)!;
  if (ancestors.length % CONSENSUS.retargetInterval !== 0) return parent.target;
  const start = ancestors[ancestors.length - CONSENSUS.retargetInterval];
  const expected = (CONSENSUS.retargetInterval - 1) * CONSENSUS.targetSeconds;
  const elapsed = Math.max(Math.floor(expected / 4), Math.min(expected * 4, parent.createdAt - start.createdAt));
  const value = BigInt(`0x${parent.target}`) * BigInt(elapsed) / BigInt(expected);
  return (value < 1n ? 1n : value > BigInt(`0x${MAX_TARGET}`) ? BigInt(`0x${MAX_TARGET}`) : value).toString(16).padStart(64, '0');
}
export function medianTime(ancestors: TestnetBlock[]): number {
  const values = ancestors.slice(-CONSENSUS.medianWindow).map(b => b.createdAt).sort((a,b) => a-b);
  return values.length ? values[Math.floor(values.length / 2)] : GENESIS_TIME;
}
export function applyTransfer(state: NftState, tx: NftTransfer, height: number): void {
  if (!transferSchema.safeParse(tx).success) throw new Error('Invalid transfer encoding/network');
  const nft = state[tx.cardHash];
  if (!nft || nft.owner !== tx.from || tx.from === tx.to || nft.sequence !== tx.sequence) throw new Error('Invalid NFT owner/sequence');
  if (height - nft.mintedHeight < CONSENSUS.coinbaseMaturity) throw new Error('NFT coinbase is immature');
  if (!verifySignature(tx.publicKey, tx.from, nftTransferMessage(tx), tx.signature)) throw new Error('Invalid transfer signature');
  state[tx.cardHash] = { ...nft, owner: tx.to, sequence: tx.sequence + 1 };
}
export function applyTransferOverlay(state: NftStateView, tx: NftTransfer, height: number): NftStateLayer {
  if (!transferSchema.safeParse(tx).success) throw new Error('Invalid transfer encoding/network');
  const nft = stateEntry(state, tx.cardHash);
  if (!nft || nft.owner !== tx.from || tx.from === tx.to || nft.sequence !== tx.sequence) {
    throw new Error('Invalid NFT owner/sequence');
  }
  if (height - nft.mintedHeight < CONSENSUS.coinbaseMaturity) throw new Error('NFT coinbase is immature');
  if (!verifySignature(tx.publicKey, tx.from, nftTransferMessage(tx), tx.signature)) throw new Error('Invalid transfer signature');
  const changes: NftState = Object.create(null) as NftState;
  changes[tx.cardHash] = { ...nft, owner: tx.to, sequence: tx.sequence + 1 };
  return { kind: 'layer', parent: state, changes };
}
export function applyTradeOverlay(state: NftStateView, trade: NftTrade, height: number): NftStateLayer {
  const parsed = tradeSchema.parse(trade);
  const allLegs = [...parsed.offered, ...parsed.requested];
  const current = allLegs.map(leg => stateEntry(state, leg.cardHash));
  if (current.some((entry, index) => !entry || entry.sequence !== allLegs[index].sequence ||
      height - entry.mintedHeight < CONSENSUS.coinbaseMaturity)) {
    throw new Error('Trade contains missing, stale, or immature NFTs');
  }
  if (current.slice(0, parsed.offered.length).some(entry => entry!.owner !== parsed.proposer) ||
      current.slice(parsed.offered.length).some(entry => entry!.owner !== parsed.counterparty)) {
    throw new Error('Trade NFT owners do not match the signed parties');
  }
  const changes: NftState = Object.create(null) as NftState;
  parsed.offered.forEach((leg, index) => {
    const nft = current[index]!;
    changes[leg.cardHash] = { ...nft, owner: parsed.counterparty, sequence: nft.sequence + 1 };
  });
  parsed.requested.forEach((leg, index) => {
    const nft = current[parsed.offered.length + index]!;
    changes[leg.cardHash] = { ...nft, owner: parsed.proposer, sequence: nft.sequence + 1 };
  });
  return { kind: 'layer', parent: state, changes };
}
export function applyTransactionOverlay(state: NftStateView, transaction: TestnetTransaction, height: number): NftStateLayer {
  return isNftTrade(transaction)
    ? applyTradeOverlay(state, transaction, height)
    : applyTransferOverlay(state, transaction, height);
}
export function transition(parent: NftStateView, header: BlockHeader, txs: TestnetTransaction[]): NftStateLayer {
  let next = parent;
  const ids = new Set<string>();
  for (const transaction of txs) {
    const id = transactionId(transaction);
    if (ids.has(id)) throw new Error('Duplicate transfer');
    ids.add(id);
    next = applyTransactionOverlay(next, transaction, header.height);
  }
  const id = mintId(header);
  if (stateEntry(next, id)) throw new Error('Duplicate NFT issuance');
  const changes: NftState = Object.create(null) as NftState;
  changes[id] = { owner: header.owner, sequence: 0, mintedHeight: header.height, pageId: header.article.pageId };
  return { kind: 'layer', parent: next, changes };
}
export function makeTemplate(ancestors: TestnetBlock[], state: NftStateView, owner: string,
  publicKey: string, transactions: TestnetTransaction[], article: Article, statsSnapshot: MintStatsSnapshot,
  now = Math.floor(Date.now()/1000)): MiningTemplate {
  if (!hex.safeParse(owner).success || address(publicKey) !== owner) throw new Error('Invalid miner identity');
  const parsedArticle = articleSchema.parse(article);
  const parsedStats = statsSnapshotSchema.parse(statsSnapshot);
  const previousHash = ancestors.at(-1)?.hash ?? GENESIS_HASH;
  const header: BlockHeader = { version: 6, network: NETWORK, chainId: CHAIN_ID,
    height: ancestors.length + 1, previousHash, createdAt: Math.max(now, medianTime(ancestors) + 1),
    article: parsedArticle, statsSnapshot: parsedStats, owner, publicKey, nonce: 0, target: expectedTarget(ancestors),
    key: expectedKey(ancestors, ancestors.length + 1), transactionsRoot: merkleRoot(transactions.map(transactionId)), stateRoot: '' };
  header.stateRoot = stateRoot(transition(state, header, transactions));
  return { header, transactions, blob: miningBlob(header).toString('hex'), nonceOffset: 32 };
}
export async function validateBlock(raw: unknown, ancestors: TestnetBlock[], parentState: NftStateView,
  pow: PowEngine, now = Math.floor(Date.now()/1000), allowHistoricalFutureTimestamp = false): Promise<{block:TestnetBlock;state:NftStateView}> {
  if (Buffer.byteLength(JSON.stringify(raw)) > CONSENSUS.maxBlockBytes) throw new Error('Block size limit exceeded');
  const b = blockSchema.parse(raw);
  if (b.height !== ancestors.length + 1 || b.previousHash !== (ancestors.at(-1)?.hash ?? GENESIS_HASH)) throw new Error('Invalid parent/height');
  if (b.createdAt <= medianTime(ancestors) || (!allowHistoricalFutureTimestamp && b.createdAt > now + CONSENSUS.maxFutureSeconds)) {
    throw new Error('Invalid block timestamp');
  }
  if (b.target !== expectedTarget(ancestors) || b.key !== expectedKey(ancestors, b.height)) throw new Error('Invalid difficulty or RandomX epoch key');
  if (b.transactionsRoot !== merkleRoot(b.transactions.map(transactionId))) throw new Error('Invalid transaction root');
  if (b.tokenId !== mintId(b)) throw new Error('Invalid NFT state commitment');
  const blob = miningBlob(b);
  if (b.hash !== sha256(blob)) throw new Error('Invalid block ID');
  if (!verifySignature(b.publicKey, b.owner, blockClaimMessage(b.hash), b.signature)) throw new Error('Invalid miner signature');
  if (BigInt(`0x${b.powHash}`) > BigInt(`0x${b.target}`)) throw new Error('Insufficient work');
  if (await pow.hash(b.key, blob) !== b.powHash) throw new Error('Invalid RandomX proof');
  // Verify native work before materializing/sorting the complete NFT state. A malformed
  // low-work block must not force O(total NFTs) commitment work on the request path.
  const next = transition(parentState, b, b.transactions);
  if (b.stateRoot !== stateRoot(next)) throw new Error('Invalid NFT state commitment');
  return { block: b, state: next };
}