/**
 * ProtomuxRPC session wrapping a HyperDHT secret stream.
 */
import ProtomuxRPC from 'protomux-rpc'
import b4a from 'b4a'
import { PROTOCOL, PROTOCOL_VERSION, Roles } from '../../shared/protocol.js'
import { encodings } from '../../shared/encodings.js'
import rateLimiter from '../utils/rateLimiter.js'
import logger from '../utils/logger.js'
import { resolveRole, assertAllowed, maxRole } from '../core/acl.js'
import { audit, shouldAudit } from '../core/audit.js'
import {
  redeemCapability,
  isPeerAllowed,
  getPeerEntry,
  registerPeer,
  touchPeer,
} from '../core/peer-policy.js'
import { validateMethodArgs, SCHEMA_VERSION } from '../../shared/schema.js'
import { verifyAdminProof } from '../../shared/crypto-auth.js'
import { getMacKey, getServerPublicKeyHex } from '../core/auth-keys.js'

export class PeerSession {
  /**
   * @param {import('stream').Duplex} stream
   * @param {{ serverPublicKey: Uint8Array, onClose?: (s: PeerSession) => void }} opts
   */
  constructor(stream, { serverPublicKey, onClose } = {}) {
    this.stream = stream
    this.id = stream.remotePublicKey
      ? b4a.toString(stream.remotePublicKey, 'hex')
      : `anon-${Date.now()}`
    this.remotePublicKey = stream.remotePublicKey
    this.closed = false
    this.onClose = onClose
    this.role = resolveRole(this.id)
    this.clientInfo = null
    this.authMode = 'viewer'
    this.displayName = null

    /** @type {Map<string, any>} */
    this.state = new Map()

    this.rpc = new ProtomuxRPC(stream, {
      id: serverPublicKey,
      protocol: PROTOCOL,
      ...encodings,
    })

    this.rpc.on('close', () => this._handleClose())
    this.rpc.on('destroy', () => this._handleClose())
    stream.on('close', () => this._handleClose())
    stream.on('error', (err) => {
      logger.error('Peer stream error', {
        peerId: this.id.slice(0, 12),
        error: err.message,
      })
    })
  }

  /**
   * @param {string} method
   * @param {(args: any, session: PeerSession) => Promise<any>|any} handler
   * @param {{ hot?: boolean }} [opts]
   */
  respond(method, handler, opts = {}) {
    const hot = opts.hot === true || rateLimiter.isStreamMethod?.(method)
    this.rpc.respond(method, encodings, async (args) => {
      if (!rateLimiter.isAllowed(this, method)) {
        const err = new Error('Rate limit exceeded. Please wait before making more requests.')
        err.code = 'RATE_LIMIT_EXCEEDED'
        throw err
      }

      if (hot) {
        try {
          assertAllowed(this.role, method)
          return await handler(args ?? {}, this)
        } catch (err) {
          if (err?.code === 'PERMISSION_DENIED') {
            audit({
              method,
              peerId: this.id,
              role: this.role,
              ok: false,
              error: err.message,
              force: true,
            })
          }
          const safe = new Error(sanitizeError(err))
          safe.code = err.code || 'UNKNOWN_ERROR'
          throw safe
        }
      }

      const t0 = Date.now()
      try {
        assertAllowed(this.role, method)
        const validated = validateMethodArgs(method, args ?? {})
        if (!validated.ok) {
          const err = new Error(validated.error || 'Invalid arguments')
          err.code = 'INVALID_ARGS'
          throw err
        }
        const result = await handler(validated.args, this)
        if (shouldAudit(method)) {
          audit({
            method,
            peerId: this.id,
            role: this.role,
            ok: true,
            args: args ?? {},
          })
        }
        const latencyMs = Date.now() - t0
        if (latencyMs >= 2000) {
          logger.warn('Slow RPC', {
            method,
            peerId: this.id.slice(0, 12),
            latencyMs,
          })
        } else {
          logger.debug('RPC ok', {
            method,
            peerId: this.id.slice(0, 12),
            latencyMs,
          })
        }
        return result
      } catch (err) {
        if (shouldAudit(method) || err?.code === 'PERMISSION_DENIED') {
          audit({
            method,
            peerId: this.id,
            role: this.role,
            ok: false,
            error: err.message,
            args: args ?? {},
            force: err?.code === 'PERMISSION_DENIED',
          })
        }
        logger.error('RPC handler failed', {
          method,
          peerId: this.id.slice(0, 12),
          role: this.role,
          error: err.message,
          code: err.code,
        })
        const safe = new Error(sanitizeError(err))
        safe.code = err.code || 'UNKNOWN_ERROR'
        throw safe
      }
    })
  }

  /**
   * @param {string} method
   * @param {unknown} payload
   */
  push(method, payload) {
    if (this.closed || this.rpc.closed) return
    this.rpc.event(method, payload, encodings)
  }

  destroy() {
    if (this.closed) return
    this.closed = true
    try {
      this.rpc.destroy()
    } catch {
      // ignore
    }
    try {
      this.stream.destroy()
    } catch {
      // ignore
    }
  }

  _handleClose() {
    if (this.closed) return
    this.closed = true
    if (this.onClose) this.onClose(this)
  }
}

/**
 * @param {PeerSession} session
 */
export function registerHandshake(session) {
  session.respond('handshake', async (args) => {
    if (args?.clientName || args?.clientVersion) {
      session.clientInfo = {
        name: args.clientName || 'unknown',
        version: args.clientVersion || null,
      }
    }

    let authMode = 'viewer'
    let elevatedRole = null

    if (args?.adminProof) {
      const serverPk = getServerPublicKeyHex()
      const proofRes = verifyAdminProof(getMacKey(), args.adminProof, {
        peerId: session.id,
        serverPublicKeyHex: serverPk || '',
      })
      if (!proofRes.ok) {
        const e = new Error(proofRes.error || 'Admin proof failed')
        e.code = proofRes.code || 'ADMIN_PROOF_FAILED'
        audit({
          method: 'handshake',
          peerId: session.id,
          role: session.role,
          ok: false,
          error: e.message,
          force: true,
        })
        throw e
      }
      elevatedRole = Roles.admin
      authMode = 'seed'
      registerPeer(session.id, { role: Roles.admin })
    }

    const capabilityToken = args?.capability || null
    if (capabilityToken && authMode !== 'seed') {
      try {
        const { role, reconnected } = redeemCapability(String(capabilityToken), session.id)
        elevatedRole = role
        authMode = reconnected ? 'registered' : 'capability'
      } catch (err) {
        const registered = getPeerEntry(session.id)
        if (registered?.role && registered.role !== Roles.viewer) {
          elevatedRole = registered.role
          authMode = 'registered'
        } else {
          const e = new Error(err.message || 'Capability redeem failed')
          e.code = err.code || 'CAPABILITY_INVALID'
          audit({
            method: 'handshake',
            peerId: session.id,
            role: session.role,
            ok: false,
            error: e.message,
            force: true,
          })
          throw e
        }
      }
    }

    if (!elevatedRole && authMode === 'viewer') {
      const registered = getPeerEntry(session.id)
      if (registered?.role) {
        elevatedRole = registered.role
        authMode = 'registered'
      }
    }

    const baseline = resolveRole(session.id)
    session.role = elevatedRole ? maxRole(baseline, elevatedRole) : baseline
    session.authMode = authMode

    if (!isPeerAllowed(session.id, { authMode })) {
      const err = new Error('Peer not allowed (revoked or not on allowlist)')
      err.code = 'PEER_DENIED'
      throw err
    }

    touchPeer(session.id)
    logger.info('Handshake complete', {
      peerId: session.id.slice(0, 12),
      role: session.role,
      authMode,
    })

    audit({
      method: 'handshake',
      peerId: session.id,
      role: session.role,
      ok: true,
      force: true,
      args: { authMode, role: session.role },
    })

    return {
      success: true,
      protocol: PROTOCOL,
      protocolVersion: PROTOCOL_VERSION,
      schemaVersion: SCHEMA_VERSION,
      role: session.role,
      peerId: session.id,
      serverTime: Date.now(),
      auth: { mode: authMode, role: session.role },
      features: {
        schemaValidation: true,
        hmacAuth: true,
        invites: true,
        room: true,
      },
    }
  })
}

function sanitizeError(err) {
  const msg = String(err?.message || err || 'Unknown error')
  return msg.length > 800 ? msg.slice(0, 800) + '…' : msg
}