#include <c_FileInputStream.h>

typedef struct {
    c_InStream_t  base;
    FILE*         fp;
    c_Allocator_t allocator;
} c_FileInImpl_t;

static c_err_t _FileIn_Read(c_InStream_t* self, void* buf, c_size_t len, c_size_t* bytes_read) {
    c_FileInImpl_t* impl = (c_FileInImpl_t*)self;
    if (!impl->fp || !buf || len == 0) return C_ERR_PARAM;

    c_size_t items = fread(buf, 1, (size_t)len, impl->fp);
    if (bytes_read) *bytes_read = items;

    if (items == 0 && ferror(impl->fp)) return C_ERR_FAIL;
    return (items == len) ? C_SUCCESS : C_ERR_OUTOFBOUND;
}

static void _FileIn_Destroy(c_InStream_t* self) {
    c_FileInImpl_t* impl = (c_FileInImpl_t*)self;
    c_Allocator_t alloc = impl->allocator;
    c_Allocator_Free(&alloc, impl);
}

static const c_InStreamVtbl_t g_FileInVtbl = { _FileIn_Read, _FileIn_Destroy };

c_err_t c_FileInputStream_Create(c_InStream_t** out_stream, FILE* file_handle, c_Allocator_t* allocator) {
    if (!out_stream || !file_handle) return C_ERR_PARAM;
    c_Allocator_t alloc = allocator ? *allocator : c_DefaultAllocator;
    c_FileInImpl_t* impl = (c_FileInImpl_t*)c_Allocator_Calloc(&alloc, 1, sizeof(c_FileInImpl_t));
    if (!impl) return C_ERR_NOMEM;

    impl->base.vtbl = &g_FileInVtbl;
    impl->fp = file_handle;
    impl->allocator = alloc;
    *out_stream = &impl->base;
    return C_SUCCESS;
}