/**
 * Postgres introspection — stage 2 of the migration pipeline.
 *
 * Produces a SchemaSnapshot from a live Kysely<Record<string, unknown>> pointing at a Postgres
 * (or pg-mem) database.
 *
 * Design notes:
 * - We deliberately avoid Kysely's built-in db.introspection.getTables() because
 *   it uses the `!~` regex operator in its internal query, which pg-mem (v3) does
 *   not support. We read information_schema directly via raw SQL instead.
 * - Primary keys come from information_schema.table_constraints +
 *   key_column_usage. Real Postgres returns rows; pg-mem (v3) returns empty rows
 *   for both views — so PK tests are gated on MIGRATE_TS_PG_URL in the test file.
 * - Default values come from information_schema.columns.column_default. pg-mem
 *   always returns null for this column, so default tests are gated too.
 * - Type normalization (pgTypeToSqlType) is exported so it can be unit-tested
 *   without a live DB.
 *
 * pg-mem gaps (documented here, gated in the test file):
 *   - information_schema.columns.character_maximum_length → always null
 *   - information_schema.columns.column_default → always null
 *   - information_schema.table_constraints / key_column_usage → empty rows
 *   - bigserial appears as "integer" (no sequence differentiation)
 *   - array_position() not implemented → pg_index catalog query throws;
 *     readPgIndexes() catches and returns [] on pg-mem
 *   - information_schema.referential_constraints not supported →
 *     readPgForeignKeys() catches and returns [] on pg-mem
 */
import type { Kysely } from "kysely";
import type { SchemaSnapshot, ColumnDefault } from "../types.js";
import type { SqlType } from "../sql-type.js";
export declare function introspectPostgres(db: Kysely<Record<string, unknown>>): Promise<SchemaSnapshot>;
/**
 * Normalise a PG column data type string into a canonical SqlType.
 * The `dataType` string comes from information_schema.columns.data_type (or
 * occasionally from information_schema.columns.udt_name).  Both are lower-cased
 * before matching.
 *
 * If character_maximum_length is available, callers should pass `maxLength`.
 *
 * `numeric` carries its qualifier OUT-OF-BAND: `data_type` is a bare "numeric"
 * for both NUMERIC and NUMERIC(9,4), so callers reading information_schema must
 * pass `numeric.precision` / `numeric.scale` (from numeric_precision /
 * numeric_scale) or the qualifier is lost. An inline "numeric(9,4)" string is
 * still parsed — that form arrives from format_type()/pg_catalog callers and
 * from unit tests — but it is NOT what information_schema produces.
 *
 * Only the numeric/decimal branch consults the qualifier: information_schema
 * also populates numeric_precision for INTEGER columns (int4 → 32, radix 2),
 * which has nothing to do with a NUMERIC qualifier.
 */
export declare function pgTypeToSqlType(dataType: string, maxLength?: number | null, udtName?: string, numeric?: {
    precision: number | null;
    scale: number | null;
}): SqlType;
/**
 * Parse a raw PG column_default string into a ColumnDefault.
 * Returns undefined if the default is absent or empty.
 *
 * Classification rules:
 *   - Expressions: now(), CURRENT_TIMESTAMP, CURRENT_DATE, CURRENT_TIME, and any
 *     bare function-call (e.g. nextval(...), gen_random_uuid(), uuid_generate_v4()),
 *     plus any value that starts with a non-quote character and contains a `::` cast
 *     (i.e. bare identifier with cast, like `NULL::text`).
 *   - Literals: `'value'` (optionally followed by `::type` cast, which PG
 *     commonly appends for clarity). The cast is stripped; the value is unquoted.
 *
 * PG stores literal booleans as `'true'::boolean`, integers as `'42'::integer`,
 * strings as `'hello'::text` — all are literals after stripping the cast.
 *
 * The bare function-call rule keeps this in lockstep with the metadata-side
 * default classifier (expected-schema's EXPR_DEFAULT_PATTERNS, which treats any
 * `()` default as an expression): without it, a `gen_random_uuid()` column default
 * round-trips as a literal here but an expression there, producing a spurious
 * column diff on every uuid-PK table.
 */
export declare function parsePgDefault(raw: string | null | undefined): ColumnDefault | undefined;
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