/* SPDX-License-Identifier: AGPL-3.0-or-later */
/* Copyright (C) 2026 David (Corey) Herrera */
/*
 * rosa.h — Suffix automaton for ROSA (Rapid Online Suffix Automaton)
 *
 * Module prefix: sa_ (suffix automaton)
 *
 * Two variants:
 *   1. sa_automaton       — binary alphabet {0,1}
 *   2. sa_token_automaton — large alphabet (vocab-sized), hash-map transitions
 *
 * Properties:
 *   - Online: O(1) amortized per symbol
 *   - At most 2*N states for sequence of length N
 *   - Longest suffix match query: O(1) amortized per step
 *
 * Reference: Blumer et al. (1985), cp-algorithms.com/string/suffix-automaton
 */

#ifndef FOUNDRY_ROSA_H
#define FOUNDRY_ROSA_H

#include <stdint.h>
#include <stdbool.h>

#ifdef __cplusplus
extern "C" {
#endif

/* ================================================================
 * Binary suffix automaton (alphabet = {0, 1})
 * ================================================================ */

typedef struct {
    int len;
    int link;
    int endpos;
    int next[2];
} sa_state;

typedef struct {
    sa_state *states;
    int n_states;
    int capacity;
    int last;
    int seq_len;
} sa_automaton;

sa_automaton* sa_new(int initial_cap);
void sa_free(sa_automaton *sa);
void sa_reset(sa_automaton *sa);
void sa_extend(sa_automaton *sa, int symbol, int position);
int  sa_query_step(sa_automaton *sa, int symbol, int *state, int *match_len);

/* ================================================================
 * Token-level suffix automaton (large alphabet, hash-map transitions)
 * ================================================================ */

typedef struct {
    int key;
    int value;
} sa_trans_entry;

typedef struct {
    int len;
    int link;
    int endpos;
    sa_trans_entry *trans;
    int trans_cap;
    int trans_count;
} sa_token_state;

typedef struct {
    sa_token_state *states;
    int n_states;
    int capacity;
    int last;
    int seq_len;
    int alphabet_size;
} sa_token_automaton;

sa_token_automaton* sa_token_new(int initial_cap, int alphabet_size);
void sa_token_free(sa_token_automaton *sa);
void sa_token_reset(sa_token_automaton *sa);
void sa_token_extend(sa_token_automaton *sa, int token, int position);
int  sa_token_query_step(sa_token_automaton *sa, int token, int *state, int *match_len);

/* ================================================================
 * Position map (SA position -> source location)
 * ================================================================ */

typedef struct {
    int conv_idx;
    int msg_idx;
    int token_offset;
} sa_position_info;

typedef struct {
    sa_position_info *entries;
    int count;
    int capacity;
} sa_position_map;

sa_position_map* sa_position_map_new(int initial_cap);
void sa_position_map_free(sa_position_map *map);
int  sa_position_map_append(sa_position_map *map, int conv_idx, int msg_idx, int token_offset);
const sa_position_info* sa_position_map_get(const sa_position_map *map, int position);

#ifdef __cplusplus
}
#endif

#endif /* FOUNDRY_ROSA_H */