#include "malunal/allocators/linear.h"

typedef struct {
  allocator_t      allocator;
  malunal_size_t   size;
  malunal_size_t   used;
  malunal_uint8_t* buffer;
} impl_t;

typedef       impl_t* impl_mptr_t;
typedef const impl_t* impl_iptr_t;
_Static_assert(
  sizeof(linear_allocator_t) == sizeof(impl_t),
  "Linear allocator must be the size of its implementation"
);

static const
allocator_vtable_t linear_allocator_vtable = {
  .acquire = (allocator_acquire_pfn_t)&linear_allocator_acquire,
  .dispose = (allocator_dispose_pfn_t)&linear_allocator_dispose
};

error_t
linear_allocator_size(
  linear_allocator_iptr_t allocator,
  malunal_uint32_t*       out
) {
  if (allocator == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NULL_ALLOCATOR
    };

  impl_mptr_t self = (impl_mptr_t)allocator;
  *out = self->size;
  return NO_ERROR;
}

error_t
linear_allocator_used(
  linear_allocator_iptr_t allocator,
  malunal_uint32_t*       out
) {
  if (allocator == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NULL_ALLOCATOR
    };

  impl_mptr_t self = (impl_mptr_t)allocator;
  *out = self->used;
  return NO_ERROR;
}

error_t
linear_allocator_init(
  malunal_size_t          size,
  malunal_mptr_t          buffer,
  linear_allocator_mptr_t allocator
) {
  if (allocator == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NULL_ALLOCATOR
    };

  impl_mptr_t self = (impl_mptr_t)allocator;
  self->allocator.vtable = &linear_allocator_vtable;
  self->buffer = buffer;
  self->size   = size;
  self->used   = 0;
  return NO_ERROR;
}

error_t
linear_allocator_acquire(
  linear_allocator_mptr_t allocator,
  malunal_size_t          size,
  malunal_mptr_t*         out
) {
  if (allocator == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NULL_ALLOCATOR
    };

  impl_mptr_t self = (impl_mptr_t)allocator;
  if (self->used + size > self->size)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_OUT_OF_MEMORY
    };

  *out = self->buffer + self->used;
  self->used += size;
  return NO_ERROR;
}

error_t
linear_allocator_dispose(
  linear_allocator_mptr_t allocator,
  malunal_mptr_t          address,
  malunal_size_t          size
) {
  if (allocator == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NULL_ALLOCATOR
    };

  impl_mptr_t self = (impl_mptr_t)allocator;

  malunal_uint8_t* addr = address;
  malunal_uint8_t* beg  = self->buffer;
  malunal_uint8_t* end  = self->buffer + self->size;
  if (addr < beg || addr > end)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NOT_MY_ADDRESS
    };

  return NO_ERROR;
}

error_t
linear_allocator_reset(
  linear_allocator_mptr_t allocator
) {
  if (allocator == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_ALLOCATOR_T,
      .code   = ALLOCATOR_ERROR_NULL_ALLOCATOR
    };

  impl_mptr_t self = (impl_mptr_t)allocator;

  self->used = 0;
  return NO_ERROR;
}