const SIMPLE_LOWER_IDENTIFIER = /^[a-z_][a-z0-9_$]*$/;

// PostgreSQL pg_get_keywords() categories R and T. GaussDB's PostgreSQL-
// compatible modes use the same identifier constraints for bare names.
const POSTGRES_RESERVED_IDENTIFIER_KEYWORDS = new Set([
  "all",
  "analyse",
  "analyze",
  "and",
  "any",
  "array",
  "as",
  "asc",
  "asymmetric",
  "authorization",
  "binary",
  "both",
  "case",
  "cast",
  "check",
  "collate",
  "collation",
  "column",
  "concurrently",
  "constraint",
  "create",
  "cross",
  "current_catalog",
  "current_date",
  "current_role",
  "current_schema",
  "current_time",
  "current_timestamp",
  "current_user",
  "default",
  "deferrable",
  "desc",
  "distinct",
  "do",
  "else",
  "end",
  "except",
  "false",
  "fetch",
  "for",
  "foreign",
  "freeze",
  "from",
  "full",
  "grant",
  "group",
  "having",
  "ilike",
  "in",
  "initially",
  "inner",
  "intersect",
  "into",
  "is",
  "isnull",
  "join",
  "lateral",
  "leading",
  "left",
  "like",
  "limit",
  "localtime",
  "localtimestamp",
  "natural",
  "not",
  "notnull",
  "null",
  "offset",
  "on",
  "only",
  "or",
  "order",
  "outer",
  "overlaps",
  "placing",
  "primary",
  "references",
  "returning",
  "right",
  "select",
  "session_user",
  "similar",
  "some",
  "symmetric",
  "system_user",
  "table",
  "tablesample",
  "then",
  "to",
  "trailing",
  "true",
  "union",
  "unique",
  "user",
  "using",
  "variadic",
  "verbose",
  "when",
  "where",
  "window",
  "with",
]);

// GaussDB MySQL-compatible drivers report a backtick. These additional words
// cover MySQL-only names that cannot safely be emitted as bare identifiers.
const MYSQL_ONLY_RESERVED_IDENTIFIER_KEYWORDS = new Set([
  "accessible",
  "auto_increment",
  "change",
  "database",
  "databases",
  "delayed",
  "describe",
  "div",
  "dual",
  "enclosed",
  "escaped",
  "explain",
  "force",
  "fulltext",
  "high_priority",
  "ignore",
  "index",
  "infile",
  "key",
  "keys",
  "kill",
  "linear",
  "lines",
  "load",
  "lock",
  "low_priority",
  "master_ssl_verify_server_cert",
  "maxvalue",
  "mediumint",
  "mod",
  "no_write_to_binlog",
  "optimize",
  "optionally",
  "outfile",
  "partition",
  "purge",
  "range",
  "read_write",
  "regexp",
  "release",
  "rename",
  "replace",
  "require",
  "rlike",
  "schema",
  "schemas",
  "separator",
  "show",
  "spatial",
  "sql_big_result",
  "sql_calc_found_rows",
  "sql_small_result",
  "ssl",
  "starting",
  "straight_join",
  "terminated",
  "tinyint",
  "unlock",
  "unsigned",
  "use",
  "utc_date",
  "utc_time",
  "utc_timestamp",
  "values",
  "varbinary",
  "varchar",
  "write",
  "xor",
  "zerofill",
]);

export function isExplicitlyQuotedSqlIdentifier(value: string): boolean {
  if (value.length < 2) return false;
  return (value.startsWith('"') && value.endsWith('"')) || (value.startsWith("`") && value.endsWith("`")) || (value.startsWith("[") && value.endsWith("]"));
}

export function requiresPostgresIdentifierQuote(identifier: string, additionalKeywords?: ReadonlySet<string>): boolean {
  if (!SIMPLE_LOWER_IDENTIFIER.test(identifier)) return true;
  return POSTGRES_RESERVED_IDENTIFIER_KEYWORDS.has(identifier) || additionalKeywords?.has(identifier) === true;
}

export function quoteGaussDbJdbcIdentifier(identifier: string, identifierQuote: string): string {
  if (isExplicitlyQuotedSqlIdentifier(identifier)) return identifier;
  const quote = identifierQuote.trim();
  if (!quote) return identifier;
  const requiresQuote = !SIMPLE_LOWER_IDENTIFIER.test(identifier) || POSTGRES_RESERVED_IDENTIFIER_KEYWORDS.has(identifier) || (quote === "`" && MYSQL_ONLY_RESERVED_IDENTIFIER_KEYWORDS.has(identifier));
  if (!requiresQuote) return identifier;
  return `${quote}${identifier.replaceAll(quote, quote + quote)}${quote}`;
}