dusk/src/dusk/asset/asset.c

/**
 * Copyright (c) 2026 Dominic Masters
 * 
 * This software is released under the MIT License.
 * https://opensource.org/licenses/MIT
 */

#include "asset.h"
#include "util/memory.h"
#include "util/string.h"
#include "assert/assert.h"
#include "engine/engine.h"
#include "util/string.h"
#include "console/console.h"
#include <unistd.h>

asset_t ASSET;

errorret_t assetInit(void) {
  memoryZero(&ASSET, sizeof(asset_t));

  for(size_t i = 0; i < ASSET_LOADING_COUNT_MAX; i++) {
    threadMutexInit(&ASSET.loading[i].mutex);
  }

  // assetInitPlatform must either define ASSET.zip or throw an error.
  errorChain(assetInitPlatform());
  assertNotNull(ASSET.zip, "Asset zip null without error.");
  threadInit(&ASSET.loadThread, assetUpdateAsync);
  threadStart(&ASSET.loadThread);

  errorOk();
}

bool_t assetFileExists(const char_t *filename) {
  assertStrLenMax(filename, ASSET_FILE_NAME_MAX, "Filename too long.");

  zip_int64_t idx = zip_name_locate(ASSET.zip, filename, 0);
  if(idx < 0) return false;
  return true;
}

assetentry_t * assetGetEntry(
  const char_t *name,
  const assetloadertype_t type,
  assetloaderinput_t *input
) {
  // Is there an existing asset?
  assetentry_t *entry = ASSET.entries;
  do {
    if(entry->type == ASSET_LOADER_TYPE_NULL) {
      entry++;
      continue;
    }
    if(stringEquals(entry->name, name)) {
      assertTrue(entry->type == type, "Asset entry type mismatch.");
      return entry;
    }
    entry++;
  } while(entry < ASSET.entries + ASSET_ENTRY_COUNT_MAX);
  
  // We did not find one existing. Find first available slot, reaping
  // zero-ref entries to make room if none are immediately available.
  bool_t reaped = false;
  for(;;) {
    entry = ASSET.entries;
    do {
      if(entry->type != ASSET_LOADER_TYPE_NULL) {
        entry++;
        continue;
      }

      if(entry->state == ASSET_ENTRY_STATE_NOT_STARTED) {
        assetEntryInit(entry, name, type, input);
        return entry;
      }
      entry++;
    } while(entry < ASSET.entries + ASSET_ENTRY_COUNT_MAX);

    if(reaped) break;
    reaped = true;
    errorCatch(assetReapUnused());
  }

  assertUnreachable("No available asset entry slots.");
  return NULL;
}

uint32_t assetGetEntriesOfType(
  assetentry_t **outEntries,
  const assetloadertype_t type
) {
  assertNotNull(outEntries, "Output entries cannot be NULL.");

  uint32_t count = 0;
  assetentry_t *entry = ASSET.entries;
  do {
    if(entry->type == type) {
      outEntries[count++] = entry;
    }
    entry++;
  } while(entry < ASSET.entries + ASSET_ENTRY_COUNT_MAX);

  return count;
}

errorret_t assetRequireLoaded(assetentry_t *entry) {
  assertNotNull(entry, "Entry cannot be NULL.");
  assertTrue(entry->type != ASSET_LOADER_TYPE_NULL, "Invalid loader type.");
  assertIsMainThread("Currently only works on main thread.");

  if(entry->state == ASSET_ENTRY_STATE_LOADED) {
    errorOk();
  }

  // Lock to prevent the reaper from collecting the entry mid-spin.
  assetEntryLock(entry);

  while(entry->state != ASSET_ENTRY_STATE_LOADED) {
    usleep(1000);
    errorret_t ret = assetUpdate();
    if(errorIsNotOk(ret)) {
      assetEntryUnlock(entry);
      errorChain(ret);
    }
  }

  assetEntryUnlock(entry);
  errorOk();
}

errorret_t assetRequireDisposed(assetentry_t *entry) {
  assertNotNull(entry, "Entry cannot be NULL.");
  assertTrue(entry->type != ASSET_LOADER_TYPE_NULL, "Invalid loader type.");
  assertIsMainThread("Currently only works on main thread.");

  if(entry->type == ASSET_LOADER_TYPE_NULL) {
    errorOk();
  }
  
  if(
    entry->state == ASSET_ENTRY_STATE_NOT_STARTED ||
    entry->state == ASSET_ENTRY_STATE_ERROR
  ) {
    errorOk();
  }
  
  assertTrue(
    entry->refs.count == 0,
    "Cannot require disposal of an entry with active references."
  );

  // Lock to prevent the reaper from collecting the entry mid-spin.
  assetEntryLock(entry);

  while(entry->type != ASSET_LOADER_TYPE_NULL) {
    usleep(1000);
    errorret_t ret = assetUpdate();
    if(errorIsNotOk(ret)) {
      assetEntryUnlock(entry);
      errorChain(ret);
    }
  }

  assetEntryUnlock(entry);
  errorOk();
}

assetentry_t * assetLock(
  const char_t *name,
  const assetloadertype_t type,
  assetloaderinput_t *input
) {
  assetentry_t *entry = assetGetEntry(name, type, input);
  assetEntryLock(entry);
  return entry;
}

void assetUnlock(const char_t *name) {
  assertNotNull(name, "Name cannot be NULL.");

  assetentry_t *entry = ASSET.entries;
  do {
    if(
      entry->type != ASSET_LOADER_TYPE_NULL &&
      stringEquals(entry->name, name)
    ) {
      assetEntryUnlock(entry);
      return;
    }
    entry++;
  } while(entry < ASSET.entries + ASSET_ENTRY_COUNT_MAX);
  
  assertUnreachable("Asset entry not found for unlock.");
}

void assetUnlockEntry(assetentry_t *entry) {
  assertNotNull(entry, "Entry cannot be NULL.");
  assetEntryUnlock(entry);
}

errorret_t assetReapUnused(void) {
  assertIsMainThread("assetReapUnused must be called from the main thread.");

  // Repeatedly find and dispose zero-ref LOADED entries until none remain.
  // This handles dependency chains where an entry (e.g. a model) holds refs
  // on child entries (mesh, texture): dispose parents first so child ref
  // counts drop to zero, then pick up the children on the next pass. Without
  // this, a forward-only scan fails when a shared child entry appears before
  // a parent that still holds a ref to it.
  bool_t any;
  do {
    any = false;
    assetentry_t *entry = ASSET.entries;
    do {
      if(entry->type == ASSET_LOADER_TYPE_NULL) { entry++; continue; }
      if(entry->state != ASSET_ENTRY_STATE_LOADED) { entry++; continue; }
      if(entry->refs.count > 0) { entry++; continue; }
      errorChain(assetEntryDispose(entry));
      any = true;
      entry++;
    } while(entry < ASSET.entries + ASSET_ENTRY_COUNT_MAX);
  } while(any);

  errorOk();
}

errorret_t assetUpdate(void) {
  assertIsMainThread("assetUpdate must be called from the main thread.");

  // Determine how many available loading slots we have.
  assetloading_t *availableLoading[ASSET_LOADING_COUNT_MAX];
  uint8_t availableLoadingCount = 0;
  assetloading_t *loading = ASSET.loading;
  assetentry_t *entry;


  do {
    // We only care about NULL entry references. Nothing async touches this so
    // it's fine to use raw here.
    if(loading->entry != NULL) {
      loading++;
      continue;
    }
    availableLoading[availableLoadingCount++] = loading;
    loading++;
  } while(loading < ASSET.loading + ASSET_LOADING_COUNT_MAX);


  // Now we can check for pending asset entries, we can't do anything if there
  // is no available slots though.
  if(availableLoadingCount > 0) {
    entry = ASSET.entries;
    do {
      // Is this asset "ready to start loading" ?
      if(entry->type == ASSET_LOADER_TYPE_NULL) {
        entry++;
        continue;
      }

      // We only care about assets not started.
      if(entry->state != ASSET_ENTRY_STATE_NOT_STARTED) {
        entry++;
        continue;
      }

      // Pop a loading slot for this asset entry.
      loading = availableLoading[--availableLoadingCount];

      // Start loading this asset.
      assetEntryStartLoading(entry, loading);
      entry++;

      // Did we run out of loading slots?
      if(availableLoadingCount == 0) {
        break;
      }
    } while(entry < ASSET.entries + ASSET_ENTRY_COUNT_MAX);
  }

  // Now walk over all the loading slots and see what needs to be done.
  loading = ASSET.loading;
  do {
    // Is the loading slot in use? Entry can only be modified synchronously.
    if(loading->entry == NULL) {
      loading++;
      continue;
    }

    // Lock the loading slot. This will prevent any async modifications.
    threadMutexLock(&loading->mutex);

    // Check the state of the entry.
    switch(loading->entry->state) {
      // This thing is pending synchronous loading.
      case ASSET_ENTRY_STATE_PENDING_SYNC:
        loading->entry->state = ASSET_ENTRY_STATE_LOADING_SYNC;
        // Unlock before calling loadSync. The sync loader may re-enter
        // assetUpdate (e.g. a script loading another asset), and the async
        // thread never touches LOADING_SYNC entries, so this is safe.
        threadMutexUnlock(&loading->mutex);

        errorret_t ret = (
          ASSET_LOADER_CALLBACKS[loading->type].loadSync(loading)
        );

        // After a sync load, these are the only valid states.
        assertTrue(
          loading->entry->state == ASSET_ENTRY_STATE_LOADED ||
          loading->entry->state == ASSET_ENTRY_STATE_ERROR ||
          loading->entry->state == ASSET_ENTRY_STATE_PENDING_SYNC ||
          loading->entry->state == ASSET_ENTRY_STATE_PENDING_ASYNC,
          "Loader did not set entry state to loaded or error on finished load."
        );

        if(errorIsNotOk(ret)) {
          errorCatch(errorPrint(ret));
          assertTrue(
            loading->entry->state == ASSET_ENTRY_STATE_ERROR,
            "Loader did not set entry state to error on failed load."
          );
        } else if(loading->entry->state == ASSET_ENTRY_STATE_LOADED) {
          assetentry_t *loadedEntry = loading->entry;
          loading->entry = NULL;
          eventInvoke(&loadedEntry->onLoaded, loadedEntry);
        }

        loading++;
        break;

      case ASSET_ENTRY_STATE_LOADING_SYNC:
        // A re-entrant assetUpdate call (e.g. from a script loading another
        // asset) will see this entry mid-sync-load. Skip it.
        threadMutexUnlock(&loading->mutex);
        loading++;
        continue;

      // Done loading, we can just free it up.
      case ASSET_ENTRY_STATE_LOADED:
        loading->entry = NULL;
        threadMutexUnlock(&loading->mutex);
        loading++;
        break;

      case ASSET_ENTRY_STATE_ERROR: {
        assetentry_t *errEntry = loading->entry;
        loading->entry = NULL;
        threadMutexUnlock(&loading->mutex);
        eventInvoke(&errEntry->onError, errEntry);
        errorThrow("Failed to load asset asynchronously.");
        break;
      }

      default:
        threadMutexUnlock(&loading->mutex);
        loading++;
        continue;
    }
  } while(loading < ASSET.loading + ASSET_LOADING_COUNT_MAX);

  errorOk();
}

void assetUpdateAsync(thread_t *thread) {
  assertNotMainThread("assetUpdateAsync must not run on the main thread.");

  while(!threadShouldStop(thread)) {
    // Walk over each asset
    assetloading_t *loading;
    loading = ASSET.loading;
    
    do {
      threadMutexLock(&loading->mutex);

      if(loading->entry == NULL) {
        threadMutexUnlock(&loading->mutex);
        loading++;
        continue;
      }

      switch(loading->entry->state) {
        case ASSET_ENTRY_STATE_PENDING_ASYNC:
          loading->entry->state = ASSET_ENTRY_STATE_LOADING_ASYNC;
          assertNotNull(
            ASSET_LOADER_CALLBACKS[loading->type].loadAsync,
            "Loader does not support async loading."
          );
          errorret_t ret = (
            ASSET_LOADER_CALLBACKS[loading->type].loadAsync(loading)
          );

          if(errorIsNotOk(ret)) {
            errorCatch(errorPrint(ret));
            assertTrue(
              loading->entry->state == ASSET_ENTRY_STATE_ERROR,
              "Loader did not set entry state to error on failed load."
            );
          }

          threadMutexUnlock(&loading->mutex);
          loading++;
          break;

        case ASSET_ENTRY_STATE_LOADING_ASYNC:
          assertUnreachable(
            "Entry is in a pending async state still?"
          );
          break;

        default:
          threadMutexUnlock(&loading->mutex);
          loading++;
          continue;
      }
    } while(loading < ASSET.loading + ASSET_LOADING_COUNT_MAX);

    if(threadShouldStop(thread)) break;
    usleep(1000);
  }
}

errorret_t assetDispose(void) {
  assertIsMainThread("Must be called from the main thread.");
  threadStop(&ASSET.loadThread);

  errorChain(assetReapUnused());

  // Cleanup zip file.
  if(ASSET.zip != NULL) {
    if(zip_close(ASSET.zip) != 0) {
      errorThrow("Failed to close asset zip archive.");
    }
    ASSET.zip = NULL;
  }

  errorChain(assetDisposePlatform());
  errorOk();
}