/**
 * meta-core client: signed claim writes (MMUR2) + plain reads.
 *
 * MIRRORED byte-for-byte across every `metamesh-plugin-*` TypeScript plugin and
 * meta-sort-core (`src/kv/meta-core-client.ts`) — guarded by
 * `scripts/check-mirrors.sh`. Edit one copy, then copy it everywhere.
 *
 * Every write is a vote signed by THIS container's key
 * (docs/implementation/metacore-claims-model.md §3, §9):
 *
 *   bytes_to_sign = "MMUR2\n" || canonical CBOR [cid, uid, key, value, ts]
 *   sig           = ECDSA-secp256k1(SHA-256(bytes)), compact r||s, low-S
 *
 * and is posted to `POST {baseUrl}/api/claims` — meta-core directly, or
 * meta-sort's pass-through relay when the plugin runs under meta-sort. The
 * encoding is pinned by meta-core's `internal/claim/testdata/claim-vectors.json`
 * (vendored as `test/claim-vectors.json`).
 *
 * Key: `METAMESH_SIGNING_KEY` (64 hex chars) or `METAMESH_SIGNING_KEY_FILE`
 * (read; generated and written 0600 if missing). With neither, writes are
 * refused (logged, return false) — no silent throwaway identities.
 *
 * Fails gracefully if meta-core is unavailable: logs and returns, never throws.
 */

import * as crypto from 'crypto';
import * as fs from 'fs';
import * as path from 'path';

// ---------------------------------------------------------------- encoding --

const DOMAIN = Buffer.from('MMUR2\n', 'utf8');
const B58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';
const N = BigInt('0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141');
const HALF_N = N >> 1n;

/** A claim value: text (public), bytes (private envelope) or null (retraction). */
export type ClaimValue = string | Uint8Array | null;

export interface SignedClaim {
    cid: string;
    uid: string;
    key: string;
    value: ClaimValue;
    ts: number;
    sig: Uint8Array;
}

function head(major: number, n: number | bigint): Buffer {
    const m = major << 5;
    const v = BigInt(n);
    if (v < 24n) return Buffer.from([m | Number(v)]);
    if (v <= 0xffn) return Buffer.from([m | 24, Number(v)]);
    if (v <= 0xffffn) {
        const b = Buffer.alloc(3);
        b[0] = m | 25;
        b.writeUInt16BE(Number(v), 1);
        return b;
    }
    if (v <= 0xffffffffn) {
        const b = Buffer.alloc(5);
        b[0] = m | 26;
        b.writeUInt32BE(Number(v), 1);
        return b;
    }
    const b = Buffer.alloc(9);
    b[0] = m | 27;
    b.writeBigUInt64BE(v, 1);
    return b;
}

function text(s: string): Buffer {
    const raw = Buffer.from(s, 'utf8');
    return Buffer.concat([head(3, raw.length), raw]);
}

/** The exact bytes an MMUR2 signature covers. */
export function signedBytes(cid: string, uid: string, key: string, value: ClaimValue, ts: number): Buffer {
    let v: Buffer;
    if (value === null) v = Buffer.from([0xf6]);
    else if (typeof value === 'string') v = text(value);
    else v = Buffer.concat([head(2, value.length), Buffer.from(value)]);
    return Buffer.concat([DOMAIN, head(4, 5), text(cid), text(uid), text(key), v, head(0, ts)]);
}

function base58Encode(bytes: Uint8Array): string {
    let n = BigInt('0x' + (Buffer.from(bytes).toString('hex') || '0'));
    let out = '';
    while (n > 0n) {
        out = B58[Number(n % 58n)] + out;
        n /= 58n;
    }
    for (const b of bytes) {
        if (b !== 0) break;
        out = '1' + out;
    }
    return out;
}

function base58Decode(s: string): Buffer {
    let n = 0n;
    for (const ch of s) {
        const i = B58.indexOf(ch);
        if (i < 0) throw new Error(`invalid base58 character ${ch}`);
        n = n * 58n + BigInt(i);
    }
    let hex = n === 0n ? '' : n.toString(16);
    if (hex.length % 2) hex = '0' + hex;
    let zeros = 0;
    while (zeros < s.length && s[zeros] === '1') zeros++;
    return Buffer.concat([Buffer.alloc(zeros), Buffer.from(hex, 'hex')]);
}

function b64url(b: Buffer): string {
    return b.toString('base64url');
}

function publicKeyFromCompressed(compressed: Buffer): crypto.KeyObject {
    const full = crypto.ECDH.convertKey(compressed, 'secp256k1', undefined, undefined, 'uncompressed') as Buffer;
    return crypto.createPublicKey({
        key: { kty: 'EC', crv: 'secp256k1', x: b64url(full.subarray(1, 33)), y: b64url(full.subarray(33, 65)) },
        format: 'jwk',
    });
}

/** Rewrite a compact signature to its low-S form (MMUR2 refuses high-S). */
function lowS(sig: Buffer): Buffer {
    const s = BigInt('0x' + sig.subarray(32).toString('hex'));
    if (s <= HALF_N) return sig;
    const fixed = Buffer.from((N - s).toString(16).padStart(64, '0'), 'hex');
    return Buffer.concat([sig.subarray(0, 32), fixed]);
}

/** True when the claim's signature is a valid low-S signature by its uid. */
export function verifyClaim(c: SignedClaim): boolean {
    try {
        const sig = Buffer.from(c.sig);
        if (sig.length !== 64) return false;
        if (BigInt('0x' + sig.subarray(32).toString('hex')) > HALF_N) return false;
        if (!c.uid.startsWith('z')) return false;
        const pub = base58Decode(c.uid.slice(1));
        if (pub.length !== 33) return false;
        return crypto.verify(
            'sha256',
            signedBytes(c.cid, c.uid, c.key, c.value, c.ts),
            { key: publicKeyFromCompressed(pub), dsaEncoding: 'ieee-p1363' },
            sig,
        );
    } catch {
        return false;
    }
}

// ----------------------------------------------------------------- signer --

export class ClaimSigner {
    readonly uid: string;
    private readonly key: crypto.KeyObject;
    private lastTs = 0;

    constructor(privateKeyHex: string) {
        const hex = privateKeyHex.trim().replace(/^0x/i, '');
        if (!/^[0-9a-fA-F]{64}$/.test(hex)) throw new Error('signing key must be 64 hex characters');
        const d = Buffer.from(hex, 'hex');
        const ecdh = crypto.createECDH('secp256k1');
        ecdh.setPrivateKey(d);
        const full = ecdh.getPublicKey(null, 'uncompressed');
        this.uid = 'z' + base58Encode(ecdh.getPublicKey(null, 'compressed'));
        this.key = crypto.createPrivateKey({
            key: {
                kty: 'EC', crv: 'secp256k1', d: b64url(d),
                x: b64url(full.subarray(1, 33)), y: b64url(full.subarray(33, 65)),
            },
            format: 'jwk',
        });
    }

    /** Milliseconds, strictly increasing within this process (ts is the version). */
    nextTs(): number {
        this.lastTs = Math.max(Date.now(), this.lastTs + 1);
        return this.lastTs;
    }

    sign(cid: string, key: string, value: ClaimValue, ts: number = this.nextTs()): SignedClaim {
        const raw = crypto.sign('sha256', signedBytes(cid, this.uid, key, value, ts), {
            key: this.key,
            dsaEncoding: 'ieee-p1363',
        });
        return { cid, uid: this.uid, key, value, ts, sig: lowS(raw) };
    }
}

let cachedSigner: ClaimSigner | null | undefined;

/**
 * The process signer from the environment, or null when no key is configured.
 * Read lazily on first write; `resetSignerForTests()` forgets it.
 */
export function loadSigner(): ClaimSigner | null {
    if (cachedSigner !== undefined) return cachedSigner;
    const inline = process.env.METAMESH_SIGNING_KEY;
    const file = process.env.METAMESH_SIGNING_KEY_FILE;
    try {
        if (inline) {
            cachedSigner = new ClaimSigner(inline);
        } else if (file) {
            if (!fs.existsSync(file)) {
                fs.mkdirSync(path.dirname(file), { recursive: true });
                fs.writeFileSync(file, crypto.randomBytes(32).toString('hex') + '\n', { mode: 0o600 });
            }
            cachedSigner = new ClaimSigner(fs.readFileSync(file, 'utf8'));
        } else {
            cachedSigner = null;
        }
    } catch (error) {
        console.warn(`[MetaCoreClient] Signing key unusable: ${error instanceof Error ? error.message : String(error)}`);
        cachedSigner = null;
    }
    if (cachedSigner) console.log(`[MetaCoreClient] Signing claims as ${cachedSigner.uid}`);
    else console.warn('[MetaCoreClient] No METAMESH_SIGNING_KEY / METAMESH_SIGNING_KEY_FILE — metadata writes are refused');
    return cachedSigner;
}

export function resetSignerForTests(): void {
    cachedSigner = undefined;
}

/** The §3.4 JSON form. */
export function claimToJSON(c: SignedClaim): Record<string, unknown> {
    let value: unknown = null;
    if (typeof c.value === 'string') value = c.value;
    else if (c.value) value = { b64: Buffer.from(c.value).toString('base64') };
    return { cid: c.cid, uid: c.uid, key: c.key, value, ts: c.ts, sig: Buffer.from(c.sig).toString('base64') };
}

// ----------------------------------------------------------------- client --

export class MetaCoreClient {
    constructor(private baseUrl: string) {}

    private async safeFetch(url: string, options: RequestInit): Promise<Response | null> {
        try {
            return await fetch(url, { ...options, signal: AbortSignal.timeout(10000) });
        } catch (error) {
            console.warn(`[MetaCoreClient] Warning: meta-core unavailable at ${this.baseUrl}: ${error instanceof Error ? error.message : String(error)}`);
            return null;
        }
    }

    /**
     * Sign and post claims about `cid`. True when every claim was accepted (or
     * was already stored: `unchanged` / `stale` are not failures).
     */
    async writeClaims(cid: string, values: Array<[string, ClaimValue]>): Promise<boolean> {
        if (values.length === 0) return true;
        const signer = loadSigner();
        if (!signer) return false;
        const claims = values.map(([key, value]) => claimToJSON(signer.sign(cid, key, value)));
        const response = await this.safeFetch(`${this.baseUrl}/api/claims`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify(claims),
        });
        if (!response) return false;
        if (!response.ok) {
            console.warn(`[MetaCoreClient] Claims for ${cid} rejected: ${response.status}`);
            return false;
        }
        const statuses = await response.json().catch(() => null) as Array<{ status?: string; reason?: string }> | null;
        const bad = (statuses ?? []).filter((s) => s.status === 'bad_signature' || s.status === 'bad_request');
        if (bad.length > 0) {
            console.warn(`[MetaCoreClient] ${bad.length} claim(s) for ${cid} refused: ${bad[0].status} ${bad[0].reason ?? ''}`);
            return false;
        }
        return true;
    }

    /** One text claim. */
    async setProperty(hashId: string, key: string, value: string): Promise<boolean> {
        return this.writeClaims(hashId, [[key, String(value)]]);
    }

    /** One text claim per entry, in a single batch. */
    async mergeMetadata(hashId: string, metadata: Record<string, string>): Promise<boolean> {
        return this.writeClaims(hashId, Object.entries(metadata).map(([k, v]) => [k, String(v)]));
    }

    /**
     * Retract this signer's own vote for `key`. Other signers' votes for the
     * same key are untouched (there are no negative votes).
     */
    async deleteProperty(hashId: string, key: string): Promise<boolean> {
        return this.writeClaims(hashId, [[key, null]]);
    }

    /**
     * Append a member to a legacy csv-set field (`genres`, `studio`, `tags`,
     * `announceList`, …) — the comma-joined shape readers still parse (the
     * METADATA_KEYS §14.12 key-set migration is out of scope for phase 1).
     *
     * Under claims a signer owns only its OWN vote, so this reads this
     * signer's current claim for (cid, key) from
     * `GET /api/meta/{cid}/claims?key=<key>` (other signers' claims are
     * ignored), adds the member if absent and signs the new full value as one
     * text claim. Members are kept raw (no escaping), same as the old
     * meta-sort `_add` proxy. A member already present writes nothing.
     */
    async addToSet(hashId: string, key: string, value: string): Promise<boolean> {
        const member = String(value);
        if (!member) return true;
        const signer = loadSigner();
        if (!signer) return false;
        const current = await this.ownClaimValue(hashId, key, signer.uid);
        if (current === undefined) return false; // could not read: never clobber our own set
        const members = current ? current.split(',').map((v) => v.trim()).filter(Boolean) : [];
        if (members.includes(member)) return true;
        return this.writeClaims(hashId, [[key, [...members, member].join(',')]]);
    }

    /**
     * This signer's newest text claim for (cid, key): the value, `null` when it
     * has none, `undefined` when the claims could not be read.
     */
    private async ownClaimValue(cid: string, key: string, uid: string): Promise<string | null | undefined> {
        const url = `${this.baseUrl}/api/meta/${encodeURIComponent(cid)}/claims?key=${encodeURIComponent(key)}`;
        const response = await this.safeFetch(url, { method: 'GET' });
        if (!response) return undefined;
        if (response.status === 404) return null;
        if (!response.ok) {
            console.warn(`[MetaCoreClient] Failed to read claims for ${cid}/${key}: ${response.status}`);
            return undefined;
        }
        const body = await response.json().catch(() => null) as unknown;
        const list = (Array.isArray(body) ? body : (body as { claims?: unknown })?.claims) as
            Array<{ uid?: string; key?: string; value?: unknown; ts?: number }> | undefined;
        let best: { value: string; ts: number } | null = null;
        for (const c of Array.isArray(list) ? list : []) {
            if (c.uid !== uid || c.key !== key || typeof c.value !== 'string') continue;
            const ts = Number(c.ts) || 0;
            if (!best || ts > best.ts) best = { value: c.value, ts };
        }
        return best ? best.value : null;
    }

    async getProperty(hashId: string, key: string): Promise<string | null> {
        const response = await this.safeFetch(`${this.baseUrl}/meta/${hashId}/${key}`, { method: 'GET' });
        if (!response || !response.ok) return null;
        const data = await response.json() as { value?: unknown };
        return data.value === undefined || data.value === null ? null : String(data.value);
    }

    /**
     * Whole merged record, in whatever form the endpoint serves (meta-sort's
     * /meta is nested, meta-core's is flat) — callers flatten. `null` when the
     * call itself failed, `{}` when the record does not exist.
     */
    async getMetadata(hashId: string): Promise<Record<string, unknown> | null> {
        const response = await this.safeFetch(`${this.baseUrl}/meta/${hashId}`, { method: 'GET' });
        if (!response) return null;
        if (response.status === 404) return {};
        if (!response.ok) return null;
        const data = await response.json() as { metadata?: Record<string, unknown> };
        return data.metadata ?? {};
    }

    /**
     * Compute the CID of a file under FILES_PATH via meta-core's `POST /file/cid`.
     * @param filePath - path relative to FILES_PATH (e.g. "poster/Movie (2024)_poster.jpg")
     */
    async computeFileCID(filePath: string): Promise<string | null> {
        const response = await this.safeFetch(`${this.baseUrl}/file/cid`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ path: filePath }),
        });
        if (!response || !response.ok) return null;
        const data = await response.json().catch(() => null) as { cid?: string } | null;
        return data?.cid ?? null;
    }
}