import { NextResponse } from 'next/server'
import { z } from 'zod'
import { validateBody } from '@/lib/api/validate'
import { withConnectorAuth, type ConnectorContext } from '@/lib/connect/hosted/with-connector-auth'
import { exchangeSkvCode, isSkvDeadRefreshTokenError, refreshSkvToken, type SkvTokenResponse } from '@/lib/connect/upstreams/skatteverket-oauth'
import { reserveUpstream } from '@/lib/connect/hosted/upstream-budget'
import { activateByPendingState, findByRefreshHash, findPendingByState, hashHandle } from '@/lib/connect/hosted/ledger'
import { verifyConnectorState } from '@/lib/connect/hosted/state'

/**
 * POST /api/connect/skv/oauth/token
 *
 * The broker exchanges an authorization code (or refreshes) with Arcim's SKV
 * client secret and returns the tokens to the instance, which stores them.
 * The ledger records only the SHA-256 of the access token (and refresh token),
 * so later data calls can prove the presenting bearer belongs to this key.
 *
 *   grant_type = authorization_code : { code, redirect_uri, code_verifier?, connector_state }
 *   grant_type = refresh_token      : { refresh_token }
 */

const AuthCodeSchema = z.object({
  grant_type: z.literal('authorization_code'),
  code: z.string().min(1).max(4096),
  redirect_uri: z.string().url().max(512),
  code_verifier: z.string().min(16).max(256).optional(),
  connector_state: z.string().min(1).max(2048),
})
const RefreshSchema = z.object({
  grant_type: z.literal('refresh_token'),
  refresh_token: z.string().min(1).max(4096),
})
const Schema = z.discriminatedUnion('grant_type', [AuthCodeSchema, RefreshSchema])

function requireScope(ctx: ConnectorContext): NextResponse | null {
  if (ctx.key.scopes.includes('skatteverket')) return null
  return NextResponse.json({ error: 'This connector key does not include Skatteverket', code: 'CONNECTOR_SCOPE_MISSING' }, { status: 403 })
}

function tokenResponse(t: SkvTokenResponse): NextResponse {
  return NextResponse.json({
    data: { access_token: t.access_token, refresh_token: t.refresh_token, expires_in: t.expires_in, scope: t.scope },
  })
}

export const POST = withConnectorAuth('connect.skv', async (request, ctx) => {
  const scopeError = requireScope(ctx)
  if (scopeError) return scopeError
  const parsed = await validateBody(request, Schema, { log: ctx.log, operation: 'connect.skv.token' })
  if (!parsed.success) return parsed.response

  const budget = await reserveUpstream(ctx.supabase, 'skatteverket')
  if (!budget.ok) {
    return NextResponse.json({ error: 'Skatteverket connector is busy', code: 'CONNECTOR_RATE_LIMITED' }, { status: 429, headers: { 'Retry-After': String(budget.retryAfterSec) } })
  }

  try {
    if (parsed.data.grant_type === 'authorization_code') {
      const { code, redirect_uri, code_verifier, connector_state } = parsed.data
      // Same binding as the bank /sessions exchange: verified state signature,
      // this key, skv service, and an existing pending row are preconditions
      // for the privileged exchange (Arcim's client secret). Without them a
      // code could be exchanged under a foreign or consumed state and live
      // tokens handed out with no ledger row proving ownership.
      const verified = verifyConnectorState(connector_state)
      if (!verified.ok) {
        return NextResponse.json({ error: 'Invalid connector state', code: 'CONNECTOR_STATE_INVALID' }, { status: 400 })
      }
      if (verified.payload.kid !== ctx.key.id || verified.payload.svc !== 'skv') {
        return NextResponse.json({ error: 'State does not belong to this key', code: 'CONNECTOR_STATE_INVALID' }, { status: 403 })
      }
      const pendingRow = await findPendingByState(ctx.supabase, { keyId: ctx.key.id, pendingState: connector_state })
      if (!pendingRow) {
        return NextResponse.json({ error: 'Unknown connection for this key', code: 'CONNECTOR_NOT_OWNED' }, { status: 404 })
      }
      const tokens = await exchangeSkvCode(code, redirect_uri, code_verifier)
      const activated = await activateByPendingState(ctx.supabase, {
        keyId: ctx.key.id,
        pendingState: connector_state,
        handle: tokens.access_token,
      })
      if (!activated) {
        // Consumed concurrently (replay of the same state): never hand out
        // tokens the ledger cannot vouch for. SKV has no revoke endpoint;
        // the unreturned pair simply expires unused.
        ctx.log.warn('skv token exchange raced a consumed state; tokens withheld')
        return NextResponse.json(
          { error: 'Connector state already consumed', code: 'CONNECTOR_STATE_CONSUMED' },
          { status: 409 },
        )
      }
      if (tokens.refresh_token) {
        // The ledger write must take before the tokens leave: a silently
        // failed update strands a connection the ledger cannot vouch for.
        const { error: hashError } = await ctx.supabase
          .from('connector_connections')
          .update({ refresh_hash: hashHandle(tokens.refresh_token) })
          .eq('connector_key_id', ctx.key.id)
          .eq('handle_hash', hashHandle(tokens.access_token))
        if (hashError) {
          ctx.log.error('skv ledger refresh-hash write failed; tokens withheld', hashError)
          return NextResponse.json({ error: 'Ledger update failed', code: 'CONNECTOR_LEDGER_FAILED' }, { status: 502 })
        }
      }
      return tokenResponse(tokens)
    }

    // refresh: ownership FIRST. The presented refresh token must hash to an
    // ACTIVE ledger row under the presenting key before the broker spends
    // Arcim's client secret on it; without this the route was an open refresh
    // oracle for any leaked refresh token. Then rotate the ledger's handle +
    // refresh hashes to the new pair. Two literal payloads (no runtime-built
    // object) so the no-phantom-columns scanner can resolve the columns.
    const { refresh_token } = parsed.data
    const oldRefreshHash = hashHandle(refresh_token)
    const owned = await findByRefreshHash(ctx.supabase, { keyId: ctx.key.id, refreshHash: oldRefreshHash })
    if (!owned) {
      return NextResponse.json({ error: 'Unknown connection for this key', code: 'CONNECTOR_NOT_OWNED' }, { status: 404 })
    }
    const tokens = await refreshSkvToken(refresh_token)
    const newHandleHash = tokens.access_token ? hashHandle(tokens.access_token) : null
    const lastUsedAt = new Date().toISOString()
    // The rotation write must take before the tokens leave: SKV has already
    // consumed the old refresh token, so a silently failed update would leave
    // a ledger that can vouch for neither the old nor the new pair.
    const { error: rotateError } = tokens.refresh_token
      ? await ctx.supabase
          .from('connector_connections')
          .update({ handle_hash: newHandleHash, last_used_at: lastUsedAt, refresh_hash: hashHandle(tokens.refresh_token) })
          .eq('id', owned.id)
          .eq('status', 'active')
      : await ctx.supabase
          .from('connector_connections')
          .update({ handle_hash: newHandleHash, last_used_at: lastUsedAt })
          .eq('id', owned.id)
          .eq('status', 'active')
    if (rotateError) {
      ctx.log.error('skv ledger rotation write failed; tokens withheld', rotateError)
      return NextResponse.json({ error: 'Ledger update failed', code: 'CONNECTOR_LEDGER_FAILED' }, { status: 502 })
    }
    return tokenResponse(tokens)
  } catch (err) {
    const message = err instanceof Error ? err.message : String(err)
    // Ordinary session expiry must be distinguishable from a transient
    // failure: SKV's per-flow refresh tokens live 65 minutes, so a dead
    // refresh token is the DOMINANT outcome here, and collapsing it into the
    // generic 502 stripped every connector instance of its reconnect flow
    // (raw 500s, no banner, cron retry spam). The instance maps this code to
    // SESSION_EXPIRED; everything else stays the opaque 502 so a transient
    // SKV outage never masquerades as "reconnect needed".
    if (parsed.data.grant_type === 'refresh_token' && isSkvDeadRefreshTokenError(message)) {
      ctx.log.info('skv refresh token expired at upstream', { code: 'CONNECTOR_SKV_REFRESH_DEAD' })
      return NextResponse.json(
        { error: 'Skatteverket refresh token is no longer valid; a new BankID consent is required', code: 'CONNECTOR_SKV_REFRESH_DEAD' },
        { status: 401 },
      )
    }
    ctx.log.warn('skv token exchange failed', { err: message })
    return NextResponse.json({ error: 'Skatteverket token exchange failed', code: 'CONNECTOR_SKV_TOKEN_FAILED' }, { status: 502 })
  }
})