/* storage.h — file backend mapping the torrent's flat byte space to files.
 *
 * A torrent is one contiguous byte space [0, total_length); this layer splits a
 * read/write at any global offset across the underlying files (a single block
 * write can straddle a file boundary). Phase 3 uses positional pread/pwrite for
 * correctness; the io_uring O_DIRECT fast path is a Phase 6 swap behind this
 * same interface. The backend is a vtable so a memory/object-store backend can
 * be registered later (the "extensible" goal).
 */
#ifndef NAUT_STORAGE_H
#define NAUT_STORAGE_H

#include "naut/common.h"
#include "naut/metainfo.h"

typedef struct naut_storage naut_storage;

typedef struct {
    bool direct_io;
    bool preallocate;
    /* Optional per-file path overrides, e.g. files moved out of `root` on a
     * prior run. If non-NULL the array has one entry per file: where overrides[i]
     * is non-NULL the file is opened at that path instead of `root`/<rel-path>,
     * so a relocated file is picked up in place (no re-download, no placeholder
     * recreated under `root`). A NULL entry uses the default location. */
    const char *const *overrides;
} naut_storage_opts;

/* Open (creating + preallocating) all files under `root`. */
naut_storage *naut_storage_open(const naut_file *files, size_t nfiles,
                                const char *root, naut_err *err);
naut_storage *naut_storage_open_opts(const naut_file *files, size_t nfiles,
                                     const char *root,
                                     const naut_storage_opts *opts,
                                     naut_err *err);
void naut_storage_close(naut_storage *s);

naut_err naut_storage_write(naut_storage *s, int64_t offset, const void *buf, size_t len);
naut_err naut_storage_read(naut_storage *s, int64_t offset, void *buf, size_t len);
naut_err naut_storage_sync(naut_storage *s);

/* Move one file to `dest` (rename, or copy+unlink across file systems) and keep
 * tracking it there: the slot's path is updated and its fd reopened, so the
 * engine can still read/write/seed the file at its new location. Typically
 * called the moment a file completes (the storage half of "move files as they
 * finish"), but safe at any time. The owning process therefore never loses
 * track of a moved file. Returns NAUT_ERR_IO if the move or reopen fails. */
naut_err naut_storage_relocate(naut_storage *s, size_t file_index, const char *dest);

int64_t naut_storage_total(const naut_storage *s);
bool    naut_storage_direct_enabled(const naut_storage *s);

#endif /* NAUT_STORAGE_H */