import type { SupabaseClient } from '@supabase/supabase-js'
import { formatRedovisningsperiod } from '@/lib/skatteverket/format'
import { resolvePeriodDates } from '@/lib/reports/vat-declaration'
import { createExtensionContext } from '@/lib/extensions/context-factory'
import type {
  SkvVatDeclarationStatusInput,
  SkvVatDeclarationStatusResult,
} from '@/lib/skatteverket/declaration-status'
import { skvRequestWithAuth, SkatteverketAuthError } from './api-client'
import { resolveReadAuth } from './resolve-auth'
import { resolveRedovisare } from './declaration-prep'
import { skvAuthCodeToStructured } from './error-map'
import { writeSkatteverketAudit } from './audit'

/**
 * Registry-resolved read service for filed momsdeklarationer (issue #1663).
 *
 * Fetches Skatteverket's /inlamnat (the declaration as submitted) and/or
 * /beslutat (the beslut) views for one period, so API consumers (v1 REST) can
 * compare their books against actually-filed data. Read-only on SKV's side;
 * the only local writes are the regulator audit rows.
 *
 * Auth follows the company-scoped read model (#1673, resolve-auth.ts): the
 * caller's own token when they connected, otherwise any other member's active
 * token, otherwise system credentials with a verified ombud grant. The fetched
 * declaration belongs to the company, not to whoever pressed "Anslut".
 *
 * Error contract: known failure modes return `{ ok: false, code, http_status,
 * error }` with structured codes so the v1 route maps them deterministically;
 * unexpected errors are thrown and handled by the route wrapper.
 */
export async function fetchVatDeclarationStatus(
  supabase: SupabaseClient,
  userId: string,
  companyId: string,
  input: SkvVatDeclarationStatusInput,
): Promise<SkvVatDeclarationStatusResult> {
  // Direct service calls bypass the HTTP dispatcher's SKATTEVERKET_ENABLED
  // gate (app/api/extensions/ext/[...path]/route.ts), so check the flag here:
  // same reasoning as the commit services in index.ts.
  if (process.env.SKATTEVERKET_ENABLED !== 'true') {
    return {
      ok: false,
      code: 'EXTENSION_DISABLED',
      http_status: 503,
      error: 'Skatteverket-integrationen är inte aktiverad i denna miljö.',
    }
  }

  const state = input.state ?? 'both'
  const ctx = createExtensionContext(supabase, userId, companyId, 'skatteverket')

  let redovisare: string
  try {
    redovisare = await resolveRedovisare(supabase, companyId)
  } catch (err) {
    // Missing org number in company settings: a configuration problem the
    // caller can fix, not a server error.
    return {
      ok: false,
      code: 'VALIDATION_ERROR',
      http_status: 400,
      error:
        err instanceof Error ? err.message : 'Organisationsnummer saknas i företagsinställningar',
    }
  }

  try {
    // Helårsmoms is filed per räkenskapsår (SFL 26 kap 10-11 §§): a broken
    // fiscal year ends in its own month, not December. Same resolution as
    // buildMomsuppgift so the period identifier matches what was filed.
    let fiscalYearEnd: { year: number; month: number } | undefined
    if (input.periodType === 'yearly') {
      const { end } = await resolvePeriodDates(
        supabase, companyId, input.periodType, input.year, input.period,
      )
      fiscalYearEnd = { year: Number(end.slice(0, 4)), month: Number(end.slice(5, 7)) }
    }
    const redovisningsperiod = formatRedovisningsperiod(
      input.periodType, input.year, input.period, fiscalYearEnd,
    )

    const resolved = await resolveReadAuth(supabase, companyId, {
      requires: 'moms_ombud',
      userId,
    })
    if (!resolved.ok) {
      return {
        ok: false,
        code: 'SKATTEVERKET_NOT_CONNECTED',
        http_status: 401,
        error:
          resolved.reason === 'needs_reconsent'
            ? 'Anslutningen mot Skatteverket behöver förnyas: Skatteverkets personliga inloggning gäller bara ca 1 timme, så detta är normalt. Be användaren ansluta igen med BankID under Inställningar → Skatteverket. Bara en person kan göra det; försök inte igen förrän användaren bekräftat.'
            : 'Inte ansluten till Skatteverket. Be användaren ansluta med BankID under Inställningar → Skatteverket.',
      }
    }

    const fetchView = async (
      view: 'inlamnat' | 'beslutat',
    ): Promise<
      | { ok: true; body: unknown }
      | { ok: false; failure: Extract<SkvVatDeclarationStatusResult, { ok: false }> }
    > => {
      const res = await skvRequestWithAuth(
        resolved.auth, 'GET', `/${view}/${redovisare}/${redovisningsperiod}`,
      )
      // Parse the 2xx body BEFORE writing the audit row, so a success status
      // with an unreadable body is recorded as skv_error, not 'ok', and maps
      // to SKATTEVERKET_API_ERROR instead of escaping as an internal 500.
      let body: unknown = null
      let bodyUnparseable = false
      if (res.ok) {
        try {
          body = await res.json()
        } catch {
          bodyUnparseable = true
        }
      }
      // 404 means "nothing on file for the period": a normal answer, not an
      // upstream failure. Same audit convention as the MCP status tool.
      const upstreamOk = (res.ok && !bodyUnparseable) || res.status === 404
      await writeSkatteverketAudit(ctx, {
        endpoint: view,
        agRegistreradId: redovisare,
        redovisningsperiod,
        outcome: upstreamOk ? 'ok' : 'skv_error',
        responseStatus: res.status,
      })
      if (res.status === 404) return { ok: true, body: null }
      if (!res.ok || bodyUnparseable) {
        // The upstream body is logged server-side only. Forwarding it verbatim
        // to API consumers would leak Skatteverket system details; the caller
        // gets the status code and a generic Swedish message.
        const text = bodyUnparseable
          ? '<2xx body was not valid JSON>'
          : await res.text().catch(() => '')
        ctx.log.warn('skv declaration-status upstream error', {
          view,
          status: res.status,
          body: text.slice(0, 500),
        })
        return {
          ok: false,
          failure: {
            ok: false,
            code: 'SKATTEVERKET_API_ERROR',
            http_status: 502,
            error: bodyUnparseable
              ? 'Skatteverket svarade med ett svar som inte kunde tolkas.'
              : `Skatteverket svarade med ${res.status}.`,
          },
        }
      }
      return { ok: true, body }
    }

    let submitted: unknown = null
    let decided: unknown = null
    if (state === 'submitted' || state === 'both') {
      const result = await fetchView('inlamnat')
      if (!result.ok) return result.failure
      submitted = result.body
    }
    if (state === 'decided' || state === 'both') {
      const result = await fetchView('beslutat')
      if (!result.ok) return result.failure
      decided = result.body
    }

    return { ok: true, redovisare, redovisningsperiod, submitted, decided }
  } catch (err) {
    if (err instanceof SkatteverketAuthError) {
      const mapped = skvAuthCodeToStructured(err.code)
      return { ok: false, code: mapped.code, http_status: mapped.httpStatus, error: err.message }
    }
    throw err
  }
}