// Signing-key lifecycle for the saltcorn-idp OIDC provider.
//
// Keys are per-tenant (stored in this tenant's _idp_keys). The private key is
// sealed at rest (AES-256-GCM under the plugin KEK); only the PUBLIC JWK is
// ever exposed, via JWKS. ensureActiveKey() is idempotent: it creates an active
// key only if none exists for the current tenant. getActiveKeyMeta() never
// touches private material so the dashboard can render without decrypting.

const db = require("@saltcorn/data/db");

const crypto    = require("./crypto");
const constants = require("./constants");


// Generate + seal a fresh RSA signing keypair and insert it as the new ACTIVE
// key. Shared by ensureActiveKey (first key for a tenant) and rotateActiveKey
// (replacement key). Returns only safe metadata; the sealed private material is
// never handed back.
const insertActiveKey = async () => {
    const kid    = crypto.newKid();
    const pair   = crypto.generateSigningKeyPair(constants.RSA_MODULUS_BITS);
    const jwk    = crypto.publicKeyToJwk(pair.publicKey, kid, constants.SIGNING_ALG);
    const pem    = crypto.exportPrivatePem(pair.privateKey);
    const sealed = crypto.sealText(pem);
    const now    = new Date().toISOString();
    const row = {
        kid:                kid,
        alg:                constants.SIGNING_ALG,
        public_jwk:         JSON.stringify(jwk),
        private_ciphertext: sealed.ciphertext,
        private_iv:         sealed.iv,
        private_tag:        sealed.tag,
        status:             constants.KEY_STATUS.ACTIVE,
        created_at:         now,
        retire_after:       null
    };
    await db.insert(constants.TABLE_KEYS, row, { noid: true });
    return { kid: kid, alg: constants.SIGNING_ALG, status: constants.KEY_STATUS.ACTIVE, created_at: now };
};


const ensureActiveKey = async () => {
    const existing = await db.selectMaybeOne(constants.TABLE_KEYS, { status: constants.KEY_STATUS.ACTIVE });
    if (existing) {
        return { kid: existing.kid, alg: existing.alg, status: existing.status, created_at: existing.created_at };
    }
    return await insertActiveKey();
};


const getJwks = async () => {
    const active   = await db.select(constants.TABLE_KEYS, { status: constants.KEY_STATUS.ACTIVE });
    const retiring = await db.select(constants.TABLE_KEYS, { status: constants.KEY_STATUS.RETIRING });
    const keys = active.concat(retiring).map((r) => JSON.parse(r.public_jwk));
    return { keys: keys };
};


const getActiveKeyMeta = async () => {
    const row = await db.selectMaybeOne(constants.TABLE_KEYS, { status: constants.KEY_STATUS.ACTIVE });
    if (!row) {
        return null;
    }
    return { kid: row.kid, alg: row.alg, created_at: row.created_at };
};


// Phase 1: decrypts and returns the private signing key for id_token signing.
const getActiveSigningKey = async () => {
    const row = await db.selectMaybeOne(constants.TABLE_KEYS, { status: constants.KEY_STATUS.ACTIVE });
    if (!row) {
        return null;
    }
    const pem = crypto.openText({
        ciphertext: row.private_ciphertext,
        iv:         row.private_iv,
        tag:        row.private_tag
    }).toString("utf8");
    return {
        kid:        row.kid,
        alg:        row.alg,
        privateKey: crypto.importPrivatePem(pem)
    };
};


// Phase 1: the active private signing key as a JWK, for oidc-provider's jwks
// config (it signs id_tokens with it and serves the public half via JWKS).
const getActivePrivateJwk = async () => {
    const key = await getActiveSigningKey();
    if (!key) {
        return null;
    }
    return crypto.privateKeyToJwk(key.privateKey, key.kid, key.alg);
};


// All non-retired private signing keys as JWKs for oidc-provider's jwks config:
// the ACTIVE key FIRST (oidc-provider signs new tokens with the first key that
// matches the requested alg) followed by any RETIRING keys, so id_tokens issued
// BEFORE a rotation still verify against JWKS during the grace window. RETIRED
// keys are excluded. This is what actually keeps a rotated-out key in /idp/jwks
// (the provider builds JWKS from this set, not from keys.getJwks()).
const getSigningPrivateJwks = async () => {
    const active   = await db.select(constants.TABLE_KEYS, { status: constants.KEY_STATUS.ACTIVE });
    const retiring = await db.select(constants.TABLE_KEYS, { status: constants.KEY_STATUS.RETIRING });
    const jwks = [];
    for (const row of active.concat(retiring)) {
        const pem = crypto.openText({
            ciphertext: row.private_ciphertext,
            iv:         row.private_iv,
            tag:        row.private_tag
        }).toString("utf8");
        jwks.push(crypto.privateKeyToJwk(crypto.importPrivatePem(pem), row.kid, row.alg));
    }
    return jwks;
};


// Flip any RETIRING keys whose grace window has elapsed to RETIRED, dropping
// them from JWKS. Idempotent and cheap; called opportunistically on the admin
// dashboard GET and at the end of a rotation. NULL retire_after never matches
// (SQL "<=" of NULL is NULL, not true), so a key without a deadline is safe.
const retireExpiredKeys = async () => {
    const now = new Date().toISOString();
    await db.updateWhere(
        constants.TABLE_KEYS,
        { status: constants.KEY_STATUS.RETIRED },
        { status: constants.KEY_STATUS.RETIRING, retire_after: { lt: now, equal: true } }
    );
};


// Admin-triggered rotation. Generates+seals a NEW ACTIVE keypair (new kid) and
// demotes the prior ACTIVE key to RETIRING with retire_after = now + the grace
// window, so id_tokens signed by the old key keep verifying (it stays in JWKS)
// until the window elapses. The OIDC Provider is built per-issuer with the
// active private JWK baked in, so its cache is cleared here to force a rebuild
// against the new key. Also sweeps any already-expired RETIRING keys to RETIRED.
const rotateActiveKey = async () => {
    const prior = await db.selectMaybeOne(constants.TABLE_KEYS, { status: constants.KEY_STATUS.ACTIVE });
    if (prior) {
        const retireAfter = new Date(Date.now() + constants.KEY_RETIRE_GRACE_MS).toISOString();
        await db.updateWhere(
            constants.TABLE_KEYS,
            { status: constants.KEY_STATUS.RETIRING, retire_after: retireAfter },
            { kid: prior.kid }
        );
    }
    const created = await insertActiveKey();
    await retireExpiredKeys();
    // Lazy-require to avoid a require cycle (provider.js requires this module).
    const { clearProviderCache } = require("./oidc/provider");
    clearProviderCache();
    return created;
};


module.exports = {
    ensureActiveKey,
    getJwks,
    getActiveKeyMeta,
    getActiveSigningKey,
    getActivePrivateJwk,
    getSigningPrivateJwks,
    rotateActiveKey,
    retireExpiredKeys
};