#ifndef WAL_INCLUDED
#define WAL_INCLUDED

#include "metadata.h"
#include "file_system.h"
#include "config.h"

typedef struct {
    MetaOper oper;
    uint32_t votes;
    int      view_number;
    uint64_t client_id;
    uint64_t request_id;
    uint32_t checksum;    // FNV-1a over all preceding fields
} WALEntry;

_Static_assert(NODE_LIMIT <= 32, "");

typedef struct {
    int       count;
    int       capacity;
    WALEntry *entries;
    Handle    handle;     // file handle to the WAL (0 = memory-only)
} WAL;

// Initialize an empty, memory-only WAL (no file backing).
void wal_init(WAL *wal);

// Initialize a WAL from an on-disk file. Recovers valid entries,
// discards partial/corrupted trailing entries. If was_truncated is
// non-NULL, *was_truncated is set to true when entries were discarded
// due to corruption (not just a partial trailing write).
int  wal_init_from_file(WAL *wal, string file, bool *was_truncated);

// Initialize a WAL from network data (memory-only, no file).
int  wal_init_from_network(WAL *wal, void *src, int num);

void wal_free(WAL *wal);

// Move ownership from src to dst. If dst is file-backed, the file
// is NOT affected; use wal_replace for atomic file replacement.
void wal_move(WAL *dst, WAL *src);

// Append an entry. If the WAL is file-backed, writes to disk and
// fsyncs before updating the in-memory buffer.
int  wal_append(WAL *wal, WALEntry entry);

// Write a modified in-memory entry back to disk (recomputes checksum).
int  wal_update_entry(WAL *wal, int idx);

// Truncate the WAL to new_count entries.
int  wal_truncate(WAL *wal, int new_count);

// Atomically replace the WAL file contents with the given entries.
// Writes to a temporary file, fsyncs, then renames over the WAL.
// Updates the in-memory buffer and reopens the file handle.
int  wal_replace(WAL *wal, WALEntry *entries, int count);

int       wal_entry_count(WAL *wal);
WALEntry *wal_peek_entry(WAL *wal, int idx);

// Persistent view_number, last_normal_view and commit_index,
// analogous to raft's TermAndVote. Backed by a small file
// ("vsr.state") with a checksum for integrity.
typedef struct {
    uint64_t view_number;
    uint64_t last_normal_view;
    int      commit_index;
    Handle   handle;
} ViewAndCommit;

int  view_and_commit_init(ViewAndCommit *vc, string file);
void view_and_commit_free(ViewAndCommit *vc);
int  set_view_and_commit(ViewAndCommit *vc, uint64_t view_number,
                         uint64_t last_normal_view, int commit_index);

#endif // WAL_INCLUDED