import { createHash } from 'node:crypto';
import {
  IMPORT_ENTITY_DEFINITIONS,
  type ImportEntity,
  type ImportFieldDefinition,
} from '@pig/core';
import type { Database } from '@pig/db';
import {
  accounts,
  contacts,
  demandDeals,
  importIdentities,
  supplyDeals,
} from '@pig/db';
import { and, eq, inArray, sql } from 'drizzle-orm';
import type { Principal } from '../lib/auth';
import { MutationError } from '../lib/mutation';
import {
  MAX_IMPORT_CELL_CHARS,
  MAX_IMPORT_COLUMNS,
  MAX_IMPORT_ROWS,
} from './tabular-import';

export type ImportTransaction = Parameters<Parameters<Database['transaction']>[0]>[0];

export interface ImportPlanInput {
  entity: ImportEntity;
  sourceName: string;
  headers: string[];
  rows: string[][];
  mapping: Record<string, string>;
  keySourceColumn: string;
}

export interface ImportRowError {
  field: string | null;
  message: string;
}

export interface ImportPreviewRow {
  rowNumber: number;
  key: string;
  action: 'create' | 'update' | 'error';
  recordId: string | null;
  values: Record<string, unknown>;
  errors: ImportRowError[];
}

export interface ImportPreview {
  digest: string;
  rows: ImportPreviewRow[];
  counts: { create: number; update: number; error: number };
}

export interface ImportCommitResult {
  created: number;
  updated: number;
  total: number;
}

type ImportDb = Database | ImportTransaction;

export class ImportService {
  constructor(private readonly db: ImportDb) {}

  async preview(input: ImportPlanInput): Promise<ImportPreview> {
    assertPlanBounds(input);
    const definition = IMPORT_ENTITY_DEFINITIONS[input.entity];
    const knownFields = new Set(definition.fields.map((field) => field.key));
    const headerSet = new Set(input.headers);
    for (const [target, source] of Object.entries(input.mapping)) {
      if (!knownFields.has(target)) throw new MutationError('invalid_mapping', `Unknown target field: ${target}.`, 400);
      if (!headerSet.has(source)) throw new MutationError('invalid_mapping', `Unknown source column: ${source}.`, 400);
    }
    if (!headerSet.has(input.keySourceColumn)) {
      throw new MutationError('invalid_mapping', 'Select a source column as the stable import key.', 400);
    }

    const keyIndex = input.headers.indexOf(input.keySourceColumn);
    const keys = input.rows.map((row) => (row[keyIndex] ?? '').trim());
    const nonemptyKeys = [...new Set(keys.filter(Boolean))];
    const identities = nonemptyKeys.length === 0
      ? []
      : await this.db
          .select()
          .from(importIdentities)
          .where(and(
            eq(importIdentities.entity, input.entity),
            eq(importIdentities.keyColumn, input.keySourceColumn),
            inArray(importIdentities.keyValue, nonemptyKeys),
          ));
    const identityByKey = new Map(identities.map((identity) => [identity.keyValue, identity]));
    const duplicateKeys = findDuplicateImportKeys(keys);

    const rows = input.rows.map((row, index): ImportPreviewRow => {
      const key = keys[index]!;
      const identity = identityByKey.get(key);
      const errors: ImportRowError[] = [];
      if (!key) errors.push({ field: null, message: 'The selected source key is blank.' });
      if (duplicateKeys.has(key)) errors.push({ field: null, message: 'The source key is duplicated in this file.' });
      const converted = convertImportRow(
        input.entity,
        input.headers,
        row,
        input.mapping,
        !identity,
      );
      errors.push(...converted.errors);
      return {
        rowNumber: index + 2,
        key,
        action: errors.length > 0 ? 'error' : identity ? 'update' : 'create',
        recordId: identity?.recordId ?? null,
        values: converted.values,
        errors,
      };
    });

    await this.validateRelationships(input.entity, rows);
    const counts = rows.reduce(
      (total, row) => ({ ...total, [row.action]: total[row.action] + 1 }),
      { create: 0, update: 0, error: 0 },
    );
    const digest = planDigest(input, rows);
    return { digest, rows, counts };
  }

  private async validateRelationships(
    entity: ImportEntity,
    previewRows: ImportPreviewRow[],
  ): Promise<void> {
    if (entity !== 'contact' && entity !== 'demand_deal' && entity !== 'supply_deal') return;
    const accountIds = [...new Set(previewRows
      .map((row) => row.values.accountId)
      .filter((value): value is string => typeof value === 'string'))];
    if (accountIds.length === 0) return;
    const found = await this.db
      .select({ id: accounts.id, side: accounts.side })
      .from(accounts)
      .where(inArray(accounts.id, accountIds));
    const accountsById = new Map(found.map((account) => [account.id, account]));
    for (const row of previewRows) {
      const accountId = row.values.accountId;
      if (typeof accountId !== 'string') continue;
      const account = accountsById.get(accountId);
      if (!account) row.errors.push({ field: 'accountId', message: 'The account does not exist.' });
      else if (entity === 'demand_deal' && account.side === 'supply') {
        row.errors.push({ field: 'accountId', message: 'A demand deal needs a demand or dual-sided account.' });
      } else if (entity === 'supply_deal' && account.side === 'demand') {
        row.errors.push({ field: 'accountId', message: 'A supply deal needs a supply or dual-sided account.' });
      }
      if (row.errors.length > 0) row.action = 'error';
    }
  }

  async commit(
    input: ImportPlanInput & { previewDigest: string },
    principal: Principal,
    now: Date,
  ): Promise<ImportCommitResult> {
    if (!('execute' in this.db)) throw new Error('Import commit requires a database transaction.');
    await this.db.execute(
      sql`select pg_advisory_xact_lock(hashtextextended(${`pig:import:${input.entity}`}, 0))`,
    );
    const preview = await this.preview(input);
    if (preview.digest !== input.previewDigest) {
      throw new MutationError(
        'stale_import_preview',
        'The import plan changed after preview. Run the dry run again before committing.',
        409,
      );
    }
    if (preview.counts.error > 0) {
      throw new MutationError(
        'invalid_import_rows',
        'Fix every row error and run the dry run again before committing.',
        409,
      );
    }

    let created = 0;
    let updated = 0;
    for (const row of preview.rows) {
      const recordId = await this.writeRecord(input.entity, row, principal, now);
      if (row.action === 'create') {
        created += 1;
        await this.db.insert(importIdentities).values({
          entity: input.entity,
          keyColumn: input.keySourceColumn,
          keyValue: row.key,
          recordId,
          importedByUserId: principal.userId,
          createdAt: now,
          updatedAt: now,
        });
      } else {
        updated += 1;
        await this.db
          .update(importIdentities)
          .set({ importedByUserId: principal.userId, updatedAt: now })
          .where(and(
            eq(importIdentities.entity, input.entity),
            eq(importIdentities.keyColumn, input.keySourceColumn),
            eq(importIdentities.keyValue, row.key),
          ));
      }
    }
    return { created, updated, total: preview.rows.length };
  }

  private async writeRecord(
    entity: ImportEntity,
    row: ImportPreviewRow,
    principal: Principal,
    now: Date,
  ): Promise<string> {
    const values = row.values;
    if (row.action === 'create') {
      if (entity === 'account') {
        const [record] = await this.db.insert(accounts).values({
          ...values,
          ownerUserId: principal.userId,
          source: 'import',
          confidence: 'unverified',
          createdAt: now,
          updatedAt: now,
        } as typeof accounts.$inferInsert).returning({ id: accounts.id });
        if (record) return record.id;
      } else if (entity === 'contact') {
        const [record] = await this.db.insert(contacts).values({
          ...values,
          ownerUserId: principal.userId,
          source: 'import',
          confidence: 'unverified',
          createdAt: now,
          updatedAt: now,
        } as typeof contacts.$inferInsert).returning({ id: contacts.id });
        if (record) return record.id;
      } else if (entity === 'demand_deal') {
        const [record] = await this.db.insert(demandDeals).values({
          ...values,
          ownerUserId: principal.userId,
          stageChangedAt: now,
          createdAt: now,
          updatedAt: now,
        } as typeof demandDeals.$inferInsert).returning({ id: demandDeals.id });
        if (record) return record.id;
      } else {
        const [record] = await this.db.insert(supplyDeals).values({
          ...values,
          ownerUserId: principal.userId,
          stageChangedAt: now,
          createdAt: now,
          updatedAt: now,
        } as typeof supplyDeals.$inferInsert).returning({ id: supplyDeals.id });
        if (record) return record.id;
      }
      throw new MutationError('write_failed', `Import row ${row.rowNumber} was not created.`, 409);
    }

    const recordId = row.recordId;
    if (!recordId) throw new MutationError('missing_import_identity', 'The import identity is incomplete.', 409);
    if (entity === 'account') {
      const [record] = await this.db.update(accounts).set({
        ...values,
        source: 'import',
        updatedAt: now,
      } as Partial<typeof accounts.$inferInsert>).where(eq(accounts.id, recordId)).returning({ id: accounts.id });
      if (record) return record.id;
    } else if (entity === 'contact') {
      const [record] = await this.db.update(contacts).set({
        ...values,
        source: 'import',
        updatedAt: now,
      } as Partial<typeof contacts.$inferInsert>).where(eq(contacts.id, recordId)).returning({ id: contacts.id });
      if (record) return record.id;
    } else if (entity === 'demand_deal') {
      const [record] = await this.db.update(demandDeals).set({
        ...values,
        updatedAt: now,
      } as Partial<typeof demandDeals.$inferInsert>).where(eq(demandDeals.id, recordId)).returning({ id: demandDeals.id });
      if (record) return record.id;
    } else {
      const [record] = await this.db.update(supplyDeals).set({
        ...values,
        updatedAt: now,
      } as Partial<typeof supplyDeals.$inferInsert>).where(eq(supplyDeals.id, recordId)).returning({ id: supplyDeals.id });
      if (record) return record.id;
    }
    throw new MutationError('missing_import_record', `The record for import row ${row.rowNumber} no longer exists.`, 409);
  }
}

export function convertImportRow(
  entity: ImportEntity,
  headers: readonly string[],
  row: readonly string[],
  mapping: Readonly<Record<string, string>>,
  isCreate: boolean,
): { values: Record<string, unknown>; errors: ImportRowError[] } {
  const values: Record<string, unknown> = {};
  const errors: ImportRowError[] = [];
  for (const field of IMPORT_ENTITY_DEFINITIONS[entity].fields) {
    const sourceColumn = mapping[field.key];
    if (!sourceColumn) {
      if (isCreate && field.required) errors.push({ field: field.key, message: `${field.label} must be mapped.` });
      continue;
    }
    const sourceIndex = headers.indexOf(sourceColumn);
    const raw = sourceIndex < 0 ? '' : (row[sourceIndex] ?? '').trim();
    if (!raw) {
      if (field.required) errors.push({ field: field.key, message: `${field.label} is required.` });
      else if (field.clearable !== false) values[field.key] = null;
      continue;
    }
    const converted = convertCell(field, raw);
    if (converted.error) errors.push({ field: field.key, message: converted.error });
    else values[field.key] = converted.value;
  }
  if (entity === 'account') {
    const side = values.side;
    if (values.supplierType && side === 'demand') {
      errors.push({ field: 'supplierType', message: 'Supplier type requires a supply or dual-sided account.' });
    }
    if (values.customerSegment && side === 'supply') {
      errors.push({ field: 'customerSegment', message: 'Customer segment requires a demand or dual-sided account.' });
    }
  }
  return { values, errors };
}

function convertCell(
  field: ImportFieldDefinition,
  raw: string,
): { value?: unknown; error?: string } {
  if (raw.length > (field.maxLength ?? MAX_IMPORT_CELL_CHARS)) {
    return { error: `${field.label} exceeds ${field.maxLength ?? MAX_IMPORT_CELL_CHARS} characters.` };
  }
  if (field.kind === 'text') return { value: raw };
  if (field.kind === 'email') {
    return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(raw)
      ? { value: raw.toLocaleLowerCase() }
      : { error: `${field.label} is not a complete email address.` };
  }
  if (field.kind === 'url') {
    try {
      const url = new URL(raw);
      return ['http:', 'https:'].includes(url.protocol)
        ? { value: url.toString() }
        : { error: `${field.label} must use http or https.` };
    } catch {
      return { error: `${field.label} is not a valid URL.` };
    }
  }
  if (field.kind === 'uuid') {
    return /^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(raw)
      ? { value: raw.toLocaleLowerCase() }
      : { error: `${field.label} must be a PIG UUID.` };
  }
  if (field.kind === 'integer') {
    if (!/^-?\d+$/.test(raw)) return { error: `${field.label} must be a whole number.` };
    const value = Number(raw);
    if (!Number.isSafeInteger(value)) return { error: `${field.label} is outside the supported range.` };
    if (field.min != null && value < field.min) return { error: `${field.label} must be at least ${field.min}.` };
    if (field.max != null && value > field.max) return { error: `${field.label} must be at most ${field.max}.` };
    return { value };
  }
  if (field.kind === 'decimal') {
    const value = Number(raw);
    if (!Number.isFinite(value)) return { error: `${field.label} must be a number.` };
    if (field.min != null && value < field.min) return { error: `${field.label} must be at least ${field.min}.` };
    if (field.max != null && value > field.max) return { error: `${field.label} must be at most ${field.max}.` };
    return { value };
  }
  if (field.kind === 'boolean') {
    const value = raw.toLocaleLowerCase();
    if (['true', 'yes', '1'].includes(value)) return { value: true };
    if (['false', 'no', '0'].includes(value)) return { value: false };
    return { error: `${field.label} must be true/false, yes/no, or 1/0.` };
  }
  if (field.kind === 'date') {
    const value = new Date(raw);
    return Number.isNaN(value.getTime())
      ? { error: `${field.label} is not a valid date.` }
      : { value };
  }
  if (field.kind === 'currency') {
    return /^[A-Za-z]{3}$/.test(raw)
      ? { value: raw.toUpperCase() }
      : { error: `${field.label} must be a three-letter currency code.` };
  }
  return field.options?.includes(raw)
    ? { value: raw }
    : { error: `${field.label} must be one of: ${field.options?.join(', ')}.` };
}

export function findDuplicateImportKeys(keys: readonly string[]): Set<string> {
  const once = new Set<string>();
  const duplicates = new Set<string>();
  for (const key of keys) {
    if (!key) continue;
    if (once.has(key)) duplicates.add(key);
    else once.add(key);
  }
  return duplicates;
}

function assertPlanBounds(input: ImportPlanInput): void {
  if (!input.sourceName.trim() || input.sourceName.length > 255) {
    throw new MutationError('invalid_import', 'The source file name is invalid.', 400);
  }
  if (input.headers.length === 0 || input.headers.length > MAX_IMPORT_COLUMNS) {
    throw new MutationError('invalid_import', 'Imports need 1–100 columns.', 400);
  }
  if (input.rows.length === 0 || input.rows.length > MAX_IMPORT_ROWS) {
    throw new MutationError('invalid_import', 'Imports need 1–2,000 data rows.', 400);
  }
  if (input.headers.some((header) => !header || header.length > 255)) {
    throw new MutationError('invalid_import', 'Source headers must be non-empty and at most 255 characters.', 400);
  }
  if (input.rows.some((row) => row.length > MAX_IMPORT_COLUMNS || row.some((cell) => cell.length > MAX_IMPORT_CELL_CHARS))) {
    throw new MutationError('invalid_import', 'The imported table exceeds the row, column, or cell limits.', 400);
  }
}

function planDigest(input: ImportPlanInput, rows: readonly ImportPreviewRow[]): string {
  const mapping = Object.fromEntries(Object.entries(input.mapping).sort(([left], [right]) => left.localeCompare(right)));
  return createHash('sha256').update(JSON.stringify({
    entity: input.entity,
    sourceName: input.sourceName,
    headers: input.headers,
    rows: input.rows,
    mapping,
    keySourceColumn: input.keySourceColumn,
    decisions: rows.map((row) => ({
      rowNumber: row.rowNumber,
      key: row.key,
      action: row.action,
      recordId: row.recordId,
      errors: row.errors,
    })),
  })).digest('hex');
}