#ifndef DATASET_HASH_H
#define DATASET_HASH_H

#include <stddef.h>
#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

// Opaque handle for hash context
typedef struct fh_context fh_context_t;

// Initialize hash context with thread pool
// num_threads: 0 = auto-detect (use number of CPU cores, capped at 8)
fh_context_t* fh_init(uint32_t num_threads);

// Cleanup context
void fh_cleanup(fh_context_t* ctx);

// Hash a single file (mmap + SIMD SHA256)
// Returns: hex string (caller frees with fh_free_string)
// Note: For batch operations, use fh_hash_directory_batch to amortize CGo overhead
char* fh_hash_file(fh_context_t* ctx, const char* path);

// Hash a directory's contents recursively and deterministically.
//
// The hash is computed over:
// - All regular files (S_ISREG) in the directory tree
// - Recursively traverses subdirectories (max depth 32)
// - Sorted lexicographically by full path for reproducibility
// - Excludes hidden files (names starting with '.')
// - Excludes symlinks, devices, and special files
//
// The combined hash is SHA256(SHA256(file1) + SHA256(file2) + ...)
// where files are processed in lexicographically sorted order.
//
// Returns: hex string (caller frees with fh_free_string), or NULL on error
char* fh_hash_directory(fh_context_t* ctx, const char* path);

// Batch hash multiple files (single CGo call for entire batch)
// paths: array of file paths
// count: number of paths
// out_hashes: pre-allocated array of 65-char buffers (64 hex + null terminator)
// Returns: 0 on success, -1 on error
int fh_hash_batch(fh_context_t* ctx, const char** paths, uint32_t count, char** out_hashes);

// Hash directory with batch output (get individual file hashes)
// out_hashes: pre-allocated array of 65-char buffers
// out_paths: optional array of path buffers (can be NULL)
// max_results: size of output arrays
// out_count: actual number of files hashed
// Returns: 0 on success, -1 on error
int fh_hash_directory_batch(
    fh_context_t* ctx,
    const char* dir_path,
    char** out_hashes,
    char** out_paths,
    uint32_t max_results,
    uint32_t* out_count
);

// Simple combined hash (single CGo call, single result)
// Best for: quick directory hash verification
// Returns: hex string (caller frees with fh_free_string)
char* fh_hash_directory_combined(fh_context_t* ctx, const char* dir_path);

// Free string returned by library
void fh_free_string(char* str);

// Constant-time hash comparison (prevents timing attacks)
// Returns: 1 if hashes are equal, 0 if not equal
// Timing is independent of the content (constant-time)
int fh_hashes_equal(const char* hash_a, const char* hash_b);

// Error handling
const char* fh_last_error(fh_context_t* ctx);
void fh_clear_error(fh_context_t* ctx);

// Configuration
void fh_set_buffer_size(fh_context_t* ctx, size_t buffer_size);
size_t fh_get_buffer_size(fh_context_t* ctx);

// SIMD detection
int fh_has_simd_sha256(void);  // Returns 1 if SIMD SHA256 available, 0 otherwise
const char* fh_get_simd_impl_name(void);  // Returns "SHA-NI", "ARMv8", or "generic"

#ifdef __cplusplus
}
#endif

#endif // DATASET_HASH_H