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// Copyright 2016 David Robillard <d@drobilla.net>
// SPDX-License-Identifier: ISC

#include "lv2/atom/atom.h"
#include "lv2/urid/urid.h"

#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>

/** Entry in an array that serves as a dictionary of properties. */
typedef struct {
  const char* uri;
  LV2_URID    urid;
  LV2_Atom*   value;
} StateMapItem;

/** Comparator for StateMapItems sorted by URID. */
static int
state_map_cmp(const void* a, const void* b)
{
  const StateMapItem* ka = (const StateMapItem*)a;
  const StateMapItem* kb = (const StateMapItem*)b;
  if (ka->urid < kb->urid) {
    return -1;
  }

  if (kb->urid < ka->urid) {
    return 1;
  }

  return 0;
}

/** Helper macro for terse state map initialisation. */
#define STATE_MAP_INIT(type, ptr) \
  (LV2_ATOM__##type), (sizeof(*(ptr)) - sizeof(LV2_Atom)), (ptr)

/**
   Initialise a state map.

   The variable parameters list must be NULL terminated, and is a sequence of
   const char* uri, const char* type, uint32_t size, LV2_Atom* value.  The
   value must point to a valid atom that resides elsewhere, the state map is
   only an index and does not contain actual state values.  The macro
   STATE_MAP_INIT can be used to make simpler code when state is composed of
   standard atom types, for example:

   struct Plugin {
       LV2_URID_Map* map;
       StateMapItem  props[3];
       // ...
   };

   state_map_init(
       self->props, self->map, self->map->handle,
       PLUG_URI "#gain",   STATE_MAP_INIT(Float,  &state->gain),
       PLUG_URI "#offset", STATE_MAP_INIT(Int,    &state->offset),
       PLUG_URI "#file",   STATE_MAP_INIT(Path,   &state->file),
       NULL);
*/
static void
state_map_init(
  StateMapItem        dict[],
  LV2_URID_Map*       map,
  LV2_URID_Map_Handle handle,
  /* const char* uri, const char* type, uint32_t size, LV2_Atom* value */...)
{
  // Set dict entries from parameters
  unsigned i = 0;
  va_list  args;
  va_start(args, handle);
  for (const char* uri = NULL; (uri = va_arg(args, const char*)); ++i) {
    const char*     type  = va_arg(args, const char*);
    const uint32_t  size  = va_arg(args, uint32_t);
    LV2_Atom* const value = va_arg(args, LV2_Atom*);
    dict[i].uri           = uri;
    dict[i].urid          = map->map(map->handle, uri);
    dict[i].value         = value;
    dict[i].value->size   = size;
    dict[i].value->type   = map->map(map->handle, type);
  }
  va_end(args);

  // Sort for fast lookup by URID by state_map_find()
  qsort(dict, i, sizeof(StateMapItem), state_map_cmp);
}

/**
   Retrieve an item from a state map by URID.

   This takes O(lg(n)) time, and is useful for implementing generic property
   access with little code, for example to respond to patch:Get messages for a
   specific property.
*/
static StateMapItem*
state_map_find(StateMapItem dict[], uint32_t n_entries, LV2_URID urid)
{
  const StateMapItem key = {NULL, urid, NULL};
  return (StateMapItem*)bsearch(
    &key, dict, n_entries, sizeof(StateMapItem), state_map_cmp);
}