const DEFAULT_ATTRIBUTION_WINDOW_MS = 10 * 60 * 1000;
const DEFAULT_SETTLEMENT_GRACE_MS = 60 * 1000;

export const REQUEST_TERMINAL_SETTLEMENT_ATTRIBUTION_STATUSES = new Set([
  'linked_settlement',
  'heuristic_match',
]);

export function deriveIntentRequestOutcomeRecords({
  preflights = [],
  submissions = [],
  inventorySnapshots = [],
  btcAsset,
  eureAsset,
  now = Date.now(),
  attributionWindowMs = DEFAULT_ATTRIBUTION_WINDOW_MS,
  settlementGraceMs = DEFAULT_SETTLEMENT_GRACE_MS,
} = {}) {
  const preflightsByRequest = new Map(
    preflights
      .map(normalizePreflight)
      .filter((entry) => entry?.request_id)
      .map((entry) => [entry.request_id, entry]),
  );
  const expectedDeltasByRequest = new Map();
  for (const preflight of preflightsByRequest.values()) {
    const expectedDelta = buildExpectedRequestDelta(preflight, null);
    if (expectedDelta) expectedDeltasByRequest.set(preflight.request_id, expectedDelta);
  }
  const activeAssetIds = uniqueAssetIds([
    ...expectedDeltasByRequest.values(),
    Object.fromEntries([btcAsset?.assetId, eureAsset?.assetId].filter(Boolean).map((assetId) => [assetId, 0n])),
  ]);
  const latestSubmissionByRequest = new Map();

  for (const submission of submissions.map(normalizeSubmission).filter(Boolean)) {
    if (!submission.request_id) continue;
    const previous = latestSubmissionByRequest.get(submission.request_id);
    if (!previous || timestampValue(submission.submitted_at) >= timestampValue(previous.submitted_at)) {
      latestSubmissionByRequest.set(submission.request_id, submission);
    }
  }

  const inventoryDeltas = deriveInventoryDeltas({
    inventorySnapshots,
    activeAssetIds,
  });
  const latestInventoryAt = latestSnapshotTimestamp(inventorySnapshots);

  return [...preflightsByRequest.values()]
    .map((preflight) => deriveOneOutcome({
      preflight,
      submission: latestSubmissionByRequest.get(preflight.request_id) || null,
      inventoryDeltas,
      latestInventoryAt,
      now,
      attributionWindowMs,
      settlementGraceMs,
    }))
    .filter(Boolean);
}

export function deriveInventoryDeltas({ inventorySnapshots = [], activeAssetIds = [] } = {}) {
  const sorted = inventorySnapshots
    .map(normalizeInventorySnapshot)
    .filter((entry) => entry?.observed_at)
    .sort((left, right) => timestampValue(left.observed_at) - timestampValue(right.observed_at));
  const deltas = [];

  for (let index = 1; index < sorted.length; index += 1) {
    const previous = sorted[index - 1];
    const current = sorted[index];
    const deltaUnits = {};
    let changed = false;

    for (const assetId of activeAssetIds) {
      const delta = safeBigInt(current.spendable?.[assetId]) - safeBigInt(previous.spendable?.[assetId]);
      deltaUnits[assetId] = delta.toString();
      if (delta !== 0n) changed = true;
    }

    if (!changed) continue;

    deltas.push({
      movement_id: `${previous.observed_at}->${current.observed_at}`,
      observed_at: current.observed_at,
      previous_observed_at: previous.observed_at,
      inventory_id: current.inventory_id,
      previous_inventory_id: previous.inventory_id,
      delta_units: deltaUnits,
    });
  }

  return deltas;
}

function deriveOneOutcome({
  preflight,
  submission,
  inventoryDeltas,
  latestInventoryAt,
  now,
  attributionWindowMs,
  settlementGraceMs,
}) {
  if (!submission) {
    return baseOutcomeRecord({
      preflight,
      submission: null,
      outcome_status: preflight.state === 'draft' ? 'draft' : 'blocked',
      outcome_observed_at: preflight.created_at,
      outcome_source: 'request_preflight',
      outcome_reason: preflight.reason_code || 'preflight_recorded',
      attribution_status: 'unattributed',
      attribution_method: null,
      attributed_inventory_delta: null,
      evidence: { preflight_state: preflight.state },
    });
  }

  if (['failed', 'blocked'].includes(submission.status)) {
    return baseOutcomeRecord({
      preflight,
      submission,
      outcome_status: submission.status,
      outcome_observed_at: submission.submitted_at,
      outcome_source: 'request_submission_result',
      outcome_reason: submission.result_code || submission.status,
      attribution_status: 'unattributed',
      attribution_method: null,
      attributed_inventory_delta: null,
      evidence: { relay_status: submission.relay_status || null },
    });
  }

  const expectedDelta = buildExpectedRequestDelta(preflight, submission);
  const matches = expectedDelta
    ? inventoryDeltas.filter((movement) => movementMatchesExpectedDelta({
      movement,
      expectedDelta,
      submittedAt: submission.submitted_at,
      attributionWindowMs,
    }))
    : [];

  if (matches.length === 1) {
    const movement = matches[0];
    return baseOutcomeRecord({
      preflight,
      submission,
      outcome_status: 'completed',
      outcome_observed_at: movement.observed_at,
      outcome_source: 'intent_inventory_spendable_delta',
      outcome_reason: 'matched_inventory_delta',
      attribution_status: 'heuristic_match',
      attribution_method: 'exact_asset_delta_within_window',
      attributed_inventory_delta: {
        inventory_id: movement.inventory_id,
        previous_inventory_id: movement.previous_inventory_id,
        observed_at: movement.observed_at,
        previous_observed_at: movement.previous_observed_at,
        delta_units: movement.delta_units,
        attribution_window_ms: attributionWindowMs,
        uncertainty:
          'Matched by exact asset-unit delta after request submission; no venue-native fill id is linked.',
      },
      evidence: {
        settlement_movement_id: movement.movement_id,
        settlement_source: 'intent_inventory_snapshots',
        relay_status: submission.relay_status || null,
      },
    });
  }

  if (matches.length > 1) {
    return baseOutcomeRecord({
      preflight,
      submission,
      outcome_status: 'awaiting_settlement',
      outcome_observed_at: submission.submitted_at,
      outcome_source: 'request_submission_and_inventory_snapshots',
      outcome_reason: 'ambiguous_inventory_delta_match',
      attribution_status: 'ambiguous',
      attribution_method: null,
      attributed_inventory_delta: null,
      evidence: {
        candidate_movement_count: matches.length,
        candidate_movement_ids: matches.map((entry) => entry.movement_id),
        relay_status: submission.relay_status || null,
      },
    });
  }

  if (submission.relay_status === 'SETTLED' && hasFreshInventoryAfterStatusCheck({ submission, latestInventoryAt })) {
    return baseOutcomeRecord({
      preflight,
      submission,
      outcome_status: 'failed',
      outcome_observed_at: latestInventoryAt || submission.status_checked_at || submission.submitted_at,
      outcome_source: 'solver_relay_status_and_inventory_snapshots',
      outcome_reason: 'relay_settled_without_expected_inventory_delta',
      attribution_status: 'unattributed',
      attribution_method: null,
      attributed_inventory_delta: null,
      evidence: {
        relay_status: submission.relay_status,
        relay_status_response: submission.relay_status_response,
        latest_inventory_observed_at: latestInventoryAt,
        uncertainty:
          'Relay reported settlement, but durable inventory did not show the expected source decrease and destination increase.',
      },
    });
  }

  if (submission.relay_status === 'NOT_FOUND_OR_NOT_VALID') {
    return baseOutcomeRecord({
      preflight,
      submission,
      outcome_status: 'not_filled',
      outcome_observed_at: submission.status_checked_at || submission.submitted_at,
      outcome_source: 'solver_relay_get_status',
      outcome_reason: 'relay_not_found_or_not_valid',
      attribution_status: 'unattributed',
      attribution_method: null,
      attributed_inventory_delta: null,
      evidence: {
        relay_status: submission.relay_status,
        relay_status_response: submission.relay_status_response,
      },
    });
  }

  const expiredWindow = getExpiredSettlementWindow({
    submission,
    preflight,
    latestInventoryAt,
    now,
    settlementGraceMs,
  });
  if (expiredWindow) {
    return baseOutcomeRecord({
      preflight,
      submission,
      outcome_status: 'not_filled',
      outcome_observed_at: expiredWindow.latestInventoryAt || expiredWindow.expiresAt || submission.submitted_at,
      outcome_source: 'request_deadline_and_inventory_snapshots',
      outcome_reason: 'deadline_elapsed_without_settlement',
      attribution_status: 'unattributed',
      attribution_method: null,
      attributed_inventory_delta: null,
      evidence: {
        deadline_at: preflight.deadline_at || null,
        settlement_grace_ms: settlementGraceMs,
        settlement_window_expired_at: expiredWindow.expiresAt,
        latest_inventory_observed_at: expiredWindow.latestInventoryAt,
        relay_status: submission.relay_status || null,
      },
    });
  }

  return baseOutcomeRecord({
    preflight,
    submission,
    outcome_status: 'awaiting_settlement',
    outcome_observed_at: submission.submitted_at,
    outcome_source: 'request_submission_result',
    outcome_reason: submission.relay_status === 'SETTLED'
      ? 'relay_settled_but_inventory_delta_missing'
      : 'accepted_by_relay_without_settlement',
    attribution_status: 'unattributed',
    attribution_method: null,
    attributed_inventory_delta: null,
    evidence: {
      relay_status: submission.relay_status || null,
      relay_status_response: submission.relay_status_response || null,
      uncertainty:
        'Relay acceptance or status is not counted as completed until inventory movement is linked.',
    },
  });
}

function buildExpectedRequestDelta(preflight, submission) {
  const destinationAmount = submission?.destination_amount_units
    || preflight?.destination_amount_units
    || preflight?.selected_quote?.amount_out
    || preflight?.quoted_destination_amount_units;
  if (!preflight?.source_asset_id || !preflight?.destination_asset_id) return null;
  if (!preflight?.source_amount_units || !destinationAmount) return null;

  return {
    [preflight.source_asset_id]: -safeBigInt(preflight.source_amount_units),
    [preflight.destination_asset_id]: safeBigInt(destinationAmount),
  };
}

function baseOutcomeRecord({
  preflight,
  submission,
  outcome_status,
  outcome_observed_at,
  outcome_source,
  outcome_reason,
  attribution_status,
  attribution_method,
  attributed_inventory_delta,
  evidence,
}) {
  const payload = {
    request_id: preflight.request_id,
    idempotency_key: preflight.idempotency_key,
    submission_id: submission?.submission_id || null,
    intent_hash: submission?.intent_hash || null,
    source_asset_id: preflight.source_asset_id,
    source_symbol: preflight.source_symbol || null,
    destination_asset_id: preflight.destination_asset_id,
    destination_symbol: preflight.destination_symbol || null,
    source_amount_units: preflight.source_amount_units,
    destination_amount_units: submission?.destination_amount_units || preflight.destination_amount_units || null,
    notional: preflight.notional || null,
    notional_asset_id: preflight.notional_asset_id || null,
    notional_symbol: preflight.notional_symbol || null,
    min_destination_amount_units: preflight.min_destination_amount_units,
    quote_hash: submission?.quote_hash || preflight.selected_quote?.quote_hash || null,
    submitted_at: submission?.submitted_at || null,
    deadline_at: preflight.deadline_at || null,
    outcome_status,
    outcome_observed_at,
    outcome_source,
    outcome_reason,
    attribution_status,
    attribution_method,
    attributed_inventory_delta,
    evidence,
  };

  return {
    request_id: preflight.request_id,
    idempotency_key: preflight.idempotency_key,
    submission_id: submission?.submission_id || null,
    intent_hash: submission?.intent_hash || null,
    submission_status: submission?.status || null,
    relay_status: submission?.relay_status || null,
    submitted_at: submission?.submitted_at || null,
    outcome_status,
    outcome_observed_at,
    outcome_source,
    outcome_reason,
    attribution_status,
    attribution_method,
    attributed_inventory_delta,
    payload,
  };
}

function movementMatchesExpectedDelta({
  movement,
  expectedDelta,
  submittedAt,
  attributionWindowMs,
}) {
  const submittedTs = timestampValue(submittedAt);
  const movementTs = timestampValue(movement.observed_at);
  if (!Number.isFinite(submittedTs) || !Number.isFinite(movementTs)) return false;
  if (movementTs < submittedTs) return false;
  if (movementTs - submittedTs > attributionWindowMs) return false;

  for (const [assetId, expected] of Object.entries(expectedDelta)) {
    if (safeBigInt(movement.delta_units?.[assetId]) !== expected) return false;
  }
  for (const [assetId, actual] of Object.entries(movement.delta_units || {})) {
    if (Object.prototype.hasOwnProperty.call(expectedDelta, assetId)) continue;
    if (safeBigInt(actual) !== 0n) return false;
  }
  return true;
}

function hasFreshInventoryAfterStatusCheck({ submission, latestInventoryAt }) {
  const statusCheckedTs = timestampValue(submission.status_checked_at || submission.submitted_at);
  const latestInventoryTs = timestampValue(latestInventoryAt);
  return Number.isFinite(statusCheckedTs)
    && Number.isFinite(latestInventoryTs)
    && latestInventoryTs >= statusCheckedTs;
}

function getExpiredSettlementWindow({
  submission,
  preflight,
  latestInventoryAt,
  now,
  settlementGraceMs,
}) {
  const submittedTs = timestampValue(submission.submitted_at);
  if (!Number.isFinite(submittedTs)) return null;

  const deadlineTs = timestampValue(preflight.deadline_at);
  const fallbackDeadlineMs = Number(preflight.min_deadline_ms || 60_000);
  const expiresAt = Number.isFinite(deadlineTs)
    ? deadlineTs + settlementGraceMs
    : submittedTs + (Number.isFinite(fallbackDeadlineMs) ? fallbackDeadlineMs : 60_000) + settlementGraceMs;
  const nowTs = typeof now === 'number' ? now : timestampValue(now);
  const latestInventoryTs = timestampValue(latestInventoryAt);

  if (
    Number.isFinite(nowTs)
    && nowTs >= expiresAt
    && Number.isFinite(latestInventoryTs)
    && latestInventoryTs >= expiresAt
  ) {
    return {
      expiresAt: new Date(expiresAt).toISOString(),
      latestInventoryAt: toIsoTimestamp(latestInventoryAt),
    };
  }
  return null;
}

function normalizePreflight(entry) {
  const payload = payloadOf(entry);
  if (!payload) return null;
  return {
    request_id: payload.request_id || entry?.request_id || null,
    idempotency_key: payload.idempotency_key || entry?.idempotency_key || null,
    state: payload.state || null,
    reason_code: payload.reason_code || null,
    source_asset_id: payload.source_asset_id || null,
    source_symbol: payload.source_symbol || null,
    destination_asset_id: payload.destination_asset_id || null,
    destination_symbol: payload.destination_symbol || null,
    source_amount_units: payload.source_amount_units || null,
    destination_amount_units: payload.destination_amount_units || null,
    notional: payload.notional || null,
    notional_asset_id: payload.notional_asset_id || null,
    notional_symbol: payload.notional_symbol || null,
    min_destination_amount_units: payload.min_destination_amount_units || null,
    quoted_destination_amount_units: payload.quoted_destination_amount_units || null,
    selected_quote: payload.selected_quote || null,
    min_deadline_ms: payload.min_deadline_ms || null,
    deadline_at: payload.deadline_at || null,
    created_at: toIsoTimestamp(
      payload.created_at
      || entry?.observed_at
      || entry?.ingested_at,
    ),
  };
}

function normalizeSubmission(entry) {
  const payload = payloadOf(entry);
  if (!payload) return null;
  return {
    request_id: payload.request_id || entry?.request_id || null,
    idempotency_key: payload.idempotency_key || entry?.idempotency_key || null,
    submission_id: payload.submission_id || null,
    status: payload.status || null,
    result_code: payload.result_code || null,
    quote_hash: payload.quote_hash || null,
    intent_hash: payload.intent_hash || null,
    destination_amount_units: payload.destination_amount_units || null,
    submitted_at: toIsoTimestamp(
      payload.submitted_at
      || entry?.observed_at
      || entry?.ingested_at,
    ),
    relay_status: payload.relay_status || null,
    relay_status_response: payload.relay_status_response || null,
    status_checked_at: payload.status_checked_at || null,
  };
}

function normalizeInventorySnapshot(entry) {
  const payload = payloadOf(entry);
  if (!payload?.spendable) return null;
  return {
    inventory_id: payload.inventory_id || null,
    observed_at: toIsoTimestamp(
      entry?.observed_at
      || entry?.ingested_at
      || payload.observed_at
      || payload.synced_at,
    ),
    spendable: payload.spendable || {},
  };
}

function latestSnapshotTimestamp(inventorySnapshots) {
  const timestamps = inventorySnapshots
    .map((entry) => normalizeInventorySnapshot(entry)?.observed_at)
    .filter(Boolean)
    .sort((left, right) => timestampValue(right) - timestampValue(left));
  return timestamps[0] || null;
}

function payloadOf(entry) {
  if (!entry) return null;
  return entry.payload || entry;
}

function uniqueAssetIds(deltaRecords = []) {
  const ids = new Set();
  for (const record of deltaRecords || []) {
    for (const assetId of Object.keys(record || {})) {
      if (assetId) ids.add(assetId);
    }
  }
  return [...ids];
}

function safeBigInt(value) {
  if (value == null || value === '') return 0n;
  return BigInt(String(value));
}

function toIsoTimestamp(value) {
  if (!value) return null;
  const date = new Date(value);
  return Number.isNaN(date.getTime()) ? null : date.toISOString();
}

function timestampValue(value) {
  const parsed = Date.parse(value || '');
  return Number.isFinite(parsed) ? parsed : NaN;
}