/**
 * @file agg_token.c
 * @brief PostgreSQL I/O functions and cast for the @c agg_token composite type.
 *
 * Implements the three SQL-callable C functions that back the
 * @c agg_token type:
 * - @c agg_token_in()   – text → agg_token (input function)
 * - @c agg_token_out()  – agg_token → text (output function)
 * - @c agg_token_cast() – agg_token → text (cast, extracts the UUID part)
 *
 * The on-wire text format is @c ( UUID , value ) where @c UUID is the
 * 36-character hyphenated UUID of the provenance gate and @c value is
 * the aggregate running value.
 */
#include "postgres.h"
#include "fmgr.h"
#include "catalog/pg_type.h"
#include "utils/uuid.h"
#include "utils/numeric.h"
#include "utils/fmgrprotos.h"
#include "executor/spi.h"
#include "access/htup_details.h"

#include "provsql_utils.h"
#include "agg_token.h"

PG_FUNCTION_INFO_V1(agg_token_in);
/**
 * @brief Parse an @c agg_token value from its text representation.
 *
 * Expected format: @c "( UUID , value )" with a single space around the
 * comma and at the outer parentheses.  Raises @c ERROR on malformed input.
 * @return Pointer to the newly allocated @c agg_token.
 */
Datum
agg_token_in(PG_FUNCTION_ARGS)
{
  char *str = PG_GETARG_CSTRING(0);
  agg_token* result;
  const unsigned toklen=sizeof(result->tok)-1;
  unsigned vallen;

  result = (agg_token *)palloc(sizeof(agg_token));

  // str is ( UUID , string ) with UUID starting at 2 and with length
  // 20 (2*UUID-LEN=16) plus 4 hashes; then three characters we can
  // ignore (two spaces and comma) then the string then two ignored
  // spaces at the end
  if(strlen(str)<toklen+7 ||
     str[0]!='(' || str[1]!=' ' || str[2+toklen] != ' ' || str[2+toklen+1] != ','
     || str[2+toklen+2] != ' ' || str[strlen(str)-2] != ' '
     || str[strlen(str)-1] != ')')
    ereport(ERROR,
            (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
             errmsg("invalid input syntax for agg_token: \"%s\"",
                    str)));

  strncpy(result->tok, str+2, toklen);
  result->tok[toklen]='\0';

  vallen=strlen(str)-toklen-2-3-2;
  if(vallen>=sizeof(result->val))
    vallen=sizeof(result->val)-1;
  strncpy(result->val, str+2+toklen+3, vallen);
  result->val[vallen]='\0';

  PG_RETURN_POINTER(result);
}

PG_FUNCTION_INFO_V1(agg_token_out);
/**
 * @brief Produce a display string for an @c agg_token.
 *
 * Default: returns @c "value (*)" (the running value followed by
 * @c " (*)"), matching @c EXPLAIN and direct @c CAST to text.
 *
 * When the @c provsql.aggtoken_text_as_uuid GUC is on, returns the
 * underlying provenance UUID instead. This is the form ProvSQL
 * Studio enables per session so agg_token cells in a result table
 * expose the circuit root UUID for click-through; the user-facing
 * @c "value (*)" string is recovered via the
 * @c provsql.agg_token_value_text(uuid) helper.
 *
 * @return C-string representation of the agg_token.
 */
Datum
agg_token_out(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  char *result;

  if (provsql_aggtoken_text_as_uuid)
    result = psprintf("%s", aggtok->tok);
  else
    result = psprintf("%s (*)", aggtok->val);

  PG_RETURN_CSTRING(result);
}

PG_FUNCTION_INFO_V1(agg_token_cast);
/**
 * @brief Cast an @c agg_token to @c text, returning only the UUID part.
 *
 * This is used when the caller needs the provenance circuit UUID
 * stored in the token rather than the aggregate value.
 * @return Text datum containing the UUID string of the token.
 */
Datum
agg_token_cast(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  char *result;
  text *txt_result;
  int len;

  result = psprintf("%s", aggtok->tok);
  len = strlen(result);

  txt_result = (text *) palloc(len + ((int32) sizeof(int32)));

  SET_VARSIZE(txt_result, len +   ((int32) sizeof(int32)));
  memcpy(VARDATA(txt_result), result, len);

  PG_RETURN_TEXT_P(txt_result);
}

/**
 * @brief True when an @c agg_token value string cannot carry a number.
 *
 * An empty or literal @c "NULL" value string (an aggregate whose value is
 * SQL NULL) must convert to SQL NULL rather than feed the type-input
 * function a string it rejects.
 */
static bool
agg_token_val_is_null(const agg_token *aggtok)
{
  return aggtok->val[0] == '\0' || strcmp(aggtok->val, "NULL") == 0;
}

PG_FUNCTION_INFO_V1(agg_token_to_numeric);
/**
 * @brief Cast an @c agg_token to @c numeric, extracting only the value.
 *
 * Emits a WARNING that provenance information is lost during the conversion.
 * @return Numeric datum parsed from the aggregate value string.
 */
Datum
agg_token_to_numeric(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  Datum result;

  provsql_warning("converting agg_token to numeric: provenance information is lost");

  if (agg_token_val_is_null(aggtok))
    PG_RETURN_NULL();

  result = DirectFunctionCall3(numeric_in,
                               CStringGetDatum(aggtok->val),
                               ObjectIdGetDatum(InvalidOid),
                               Int32GetDatum(-1));
  PG_RETURN_DATUM(result);
}

PG_FUNCTION_INFO_V1(agg_token_value);
/**
 * @brief Extract the running value of an @c agg_token as @c numeric.
 *
 * Unlike @c agg_token_to_numeric, this does @b not emit the
 * "provenance information is lost" warning: it is the internal accessor
 * used by the provenance-preserving @c agg_token arithmetic operators
 * (which keep the provenance in a @c gate_arith circuit), where no
 * provenance is dropped.
 * @return Numeric datum parsed from the aggregate value string.
 */
Datum
agg_token_value(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  Datum result;

  if (agg_token_val_is_null(aggtok))
    PG_RETURN_NULL();

  result = DirectFunctionCall3(numeric_in,
                               CStringGetDatum(aggtok->val),
                               ObjectIdGetDatum(InvalidOid),
                               Int32GetDatum(-1));
  PG_RETURN_DATUM(result);
}

PG_FUNCTION_INFO_V1(agg_token_to_float8);
/**
 * @brief Cast an @c agg_token to @c double precision, extracting only the value.
 *
 * Emits a WARNING that provenance information is lost during the conversion.
 * @return Float8 datum parsed from the aggregate value string.
 */
Datum
agg_token_to_float8(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  Datum result;

  provsql_warning("converting agg_token to double precision: provenance information is lost");

  if (agg_token_val_is_null(aggtok))
    PG_RETURN_NULL();

  result = DirectFunctionCall1(float8in,
                               CStringGetDatum(aggtok->val));
  PG_RETURN_DATUM(result);
}

PG_FUNCTION_INFO_V1(agg_token_to_int4);
/**
 * @brief Cast an @c agg_token to @c integer, extracting only the value.
 *
 * Emits a WARNING that provenance information is lost during the conversion.
 * @return Int32 datum parsed from the aggregate value string.
 */
Datum
agg_token_to_int4(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  Datum result;

  provsql_warning("converting agg_token to integer: provenance information is lost");

  if (agg_token_val_is_null(aggtok))
    PG_RETURN_NULL();

  result = DirectFunctionCall1(int4in,
                               CStringGetDatum(aggtok->val));
  PG_RETURN_DATUM(result);
}

PG_FUNCTION_INFO_V1(agg_token_to_int8);
/**
 * @brief Cast an @c agg_token to @c bigint, extracting only the value.
 *
 * Emits a WARNING that provenance information is lost during the conversion.
 * @return Int64 datum parsed from the aggregate value string.
 */
Datum
agg_token_to_int8(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  Datum result;

  provsql_warning("converting agg_token to bigint: provenance information is lost");

  if (agg_token_val_is_null(aggtok))
    PG_RETURN_NULL();

  result = DirectFunctionCall1(int8in,
                               CStringGetDatum(aggtok->val));
  PG_RETURN_DATUM(result);
}

PG_FUNCTION_INFO_V1(agg_token_to_text);
/**
 * @brief Cast an @c agg_token to @c text, extracting only the value.
 *
 * Unlike @c agg_token_cast which returns the UUID part, this returns
 * the aggregate value as text.
 * Emits a WARNING that provenance information is lost during the conversion.
 * @return Text datum containing the aggregate value string.
 */
Datum
agg_token_to_text(PG_FUNCTION_ARGS)
{
  agg_token *aggtok = (agg_token *) PG_GETARG_POINTER(0);
  text *txt_result;
  int len;

  provsql_warning("converting agg_token to text: provenance information is lost");

  len = strlen(aggtok->val);
  txt_result = (text *) palloc(len + VARHDRSZ);
  SET_VARSIZE(txt_result, len + VARHDRSZ);
  memcpy(VARDATA(txt_result), aggtok->val, len);

  PG_RETURN_TEXT_P(txt_result);
}