bantam-cpp/bantam.hpp

/* Bantam: tiny, powerful, DIY AI agent — modern C++20 port
 * Created by Luxferre in 2026, released into the public domain.
 *
 * This is a C++20 rewrite of the pure-C port (bantam-c). It talks to any
 * OpenAI-compatible /chat/completions API and implements the same agentic
 * loop, tools, session management, markdown terminal rendering and
 * raw-terminal line editor.
 *
 * Design goals relative to the C port:
 *   - Use standard, safe C++ containers (std::string, std::vector,
 *     std::map, std::span) instead of raw memory areas.
 *   - Eliminate hand-rolled allocation/string code; rely on RAII so there
 *     is far less room for memory-allocation related vulnerabilities.
 *   - Depend only on libcurl (HTTP) and GNU readline (interactive line
 *     editing); JSON parsing/serialization and Markdown rendering are
 *     implemented natively in modern C++20 with zero external bloat.
 *
 * Feature macros: we rely on POSIX.1-2008 interfaces. */
#ifndef BANTAM_HPP
#define BANTAM_HPP

#include <cstdarg>
#include <cstdio>
#include <cstddef>
#include <cstdint>
#include <map>
#include <memory>
#include <span>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

/* ------------------------------------------------------------------ */
/* Minimal RFC 8259 JSON value, parser and serializer (json.cpp).      */
/* ------------------------------------------------------------------ */
enum class JType { Null, Bool, Int, Float, Str, Arr, Obj };

struct Json {
  JType type = JType::Null;
  bool bval = false;
  int64_t ival = 0;
  double dval = 0.0;
  std::string sval;
  std::vector<Json> aval;
  std::vector<std::pair<std::string, Json>> oval;

  Json();
  ~Json();
  Json(const Json &);
  Json(Json &&) noexcept;
  Json &operator=(const Json &);
  Json &operator=(Json &&) noexcept;

  Json(std::nullptr_t);
  Json(bool b);
  Json(int n);
  Json(int64_t n);
  Json(double d);
  Json(const char *s);
  Json(std::string s);
  Json(std::string_view s);

  static Json object();
  static Json array();

  bool is_null() const { return type == JType::Null; }
  bool is_bool() const { return type == JType::Bool; }
  bool is_number_integer() const { return type == JType::Int; }
  bool is_number() const { return type == JType::Int || type == JType::Float; }
  bool is_string() const { return type == JType::Str; }
  bool is_array() const { return type == JType::Arr; }
  bool is_object() const { return type == JType::Obj; }

  bool empty() const;
  size_t size() const;
  bool contains(std::string_view k) const;
  Json &operator[](std::string_view k);
  const Json &operator[](std::string_view k) const;
  Json &at(size_t i);
  const Json &at(size_t i) const;
  void push_back(Json v);

  std::string str(std::string_view def = "") const;
  int64_t as_int64(int64_t def = 0) const;
  int as_int(int def = 0) const;

  std::string dump(int indent = -1) const;
  static bool parse(std::string_view src, Json &out);
};

/* Markdown renderer state (code-fence tracking). */
struct MdState {
  bool in_code = false;
};

/* ------------------------------------------------------------------ */
/* Tool call / message / usage / config structures.                    */
/* ------------------------------------------------------------------ */
struct ToolCall {
  std::string id;
  std::string name;
  std::string arguments; /* raw JSON text of the arguments object */
};

struct Message {
  std::string role;
  std::string content;      /* empty when absent */
  std::string reasoning;    /* empty when absent */
  std::vector<ToolCall> calls;
  std::string tool_call_id; /* empty when absent (tool role only) */
  int calls_shown = 0;
};

struct Messages {
  std::vector<Message> items;
};

struct Usage {
  int prompt_tokens = 0;
  int completion_tokens = 0;
  int total_tokens = 0;
  int cached_tokens = 0;
  int context_tokens = 0;
  std::string model;
};

struct Cfg {
  std::string endpoint;
  std::string model;
  std::string api_key;
  std::string color;
  double temperature = 0.7;
  int timeout = 300;
  int shell_timeout = 120;
  int max_al_iterations = 1000;
  int stream = 1;          /* 0/1 */
  int force_stream = -1;   /* -1 = auto, 0/1 = force (compaction) */
  int context_window = 262144;
  int max_tool_res = 65536;
  bool context_window_set = false;
  std::map<std::string, std::string> raw; /* raw key/value map */
};

struct Session {
  std::string id;
  std::string created;
  std::string summary;
  Messages messages;
};

/* ------------------------------------------------------------------ */
/* Globals.                                                            */
/* ------------------------------------------------------------------ */
extern int g_col;                  /* color enabled (0/1) */
extern volatile int g_interrupted; /* SIGINT flag */

/* ------------------------------------------------------------------ */
/* util.cpp                                                            */
/* ------------------------------------------------------------------ */
void setup_signal_handler();
int is_terminal(int fd);
int to_int_val(std::string_view s, int def);
bool read_file_str(std::string_view path, std::string &out);
bool write_file_str(std::string_view path, std::string_view data);

std::string sfmt(const char *fmt, ...);
void str_appendf(std::string &s, const char *fmt, ...);

/* UTF-8 helpers. */
int utf8_decode(const unsigned char *p, size_t avail, size_t *plen);
std::string_view utf8_truncate(std::string_view s, size_t max_bytes);

std::string filter_text(std::string_view s);
int color_enabled(const Cfg &cfg);
template<class R>
inline std::string cstr(std::string_view text, const R& codes) {
  if (!g_col || codes.empty() || text.empty()) return std::string(text);
  std::string s;
  s.reserve(text.size() + 16);
  s += "\033[";
  for (size_t i = 0; i < codes.size(); i++) {
    if (i) s += ';';
    int v = (int)codes[i];
    if (v <= 0) {
      s += '0';
    } else {
      char rev[12];
      int rn = 0;
      while (v > 0 && rn < 12) { rev[rn++] = (char)('0' + (v % 10)); v /= 10; }
      while (rn > 0) s += rev[--rn];
    }
  }
  s += 'm';
  s += text;
  s += "\033[0m";
  return s;
}
template<class R>
inline void cprint(std::string_view text, const R& codes) {
  if (text.empty()) return;
  if (!g_col || codes.empty()) {
    std::fwrite(text.data(), 1, text.size(), stdout);
    return;
  }
  char seq[32];
  size_t pos = 0;
  seq[pos++] = '\033';
  seq[pos++] = '[';
  for (size_t i = 0; i < codes.size() && pos + 12 < sizeof(seq); i++) {
    if (i) seq[pos++] = ';';
    int v = (int)codes[i];
    if (v <= 0) {
      seq[pos++] = '0';
    } else {
      char rev[12];
      int rn = 0;
      while (v > 0 && rn < 12) { rev[rn++] = (char)('0' + (v % 10)); v /= 10; }
      while (rn > 0) seq[pos++] = rev[--rn];
    }
  }
  seq[pos++] = 'm';
  std::fwrite(seq, 1, pos, stdout);
  std::fwrite(text.data(), 1, text.size(), stdout);
  std::fwrite("\033[0m", 1, 4, stdout);
}
int visible_len(std::string_view s);
int rune_width(int cp);

void mkdir_p(std::string_view dir);
std::string project_id();
std::string bantam_tmp_dir(std::string_view sess_id = "");
std::string tool_res_dir(std::string_view sess_id = "");
std::string md5_hex(std::string_view data);

/* ------------------------------------------------------------------ */
/* config.cpp                                                          */
/* ------------------------------------------------------------------ */
const std::string *cfg_raw_get(const Cfg &c, std::string_view k);
bool internal_key(std::string_view k);
Cfg get_cfg(std::string_view path);
int set_cfg(std::string_view path, std::string_view key, std::string_view val);
std::string config_path();
int fetch_context_window(Cfg &cfg);
std::string list_models(Cfg &cfg, int *errout);
std::string tools_dir(const Cfg &c);
std::string skills_dir(const Cfg &c);

/* ------------------------------------------------------------------ */
/* json.cpp — JSON engine, request building & response parsing.        */
/* ------------------------------------------------------------------ */
void serialize_message_json(Json &obj, const Message &m);
void parse_message_json(const Json &obj, Message &m);
std::string build_request_json(const Cfg &cfg, const Messages &msgs,
                               bool use_tools, bool stream);
bool parse_nonstream_response(std::string_view body, Message &out, Usage &usage);

/* ------------------------------------------------------------------ */
/* llm.cpp — HTTP client (libcurl), headers, backoff, dispatch.        */
/* ------------------------------------------------------------------ */
void http_cleanup();
int http_get(Cfg &cfg, std::string_view url, std::string &body, long &code,
             std::string &errmsg);
int llm(Cfg &cfg, Messages &msgs, bool use_tools, Message &out, Usage &usage,
        std::string &errmsg, volatile int *interrupted);

/* ------------------------------------------------------------------ */
/* tools.cpp                                                           */
/* ------------------------------------------------------------------ */
std::string shell_with_workdir(std::string_view cmd, std::string_view workdir,
                               int timeout, volatile int *interrupted);
std::string read_file_or_dir(std::string_view path, int offset, int limit,
                             int *style);
std::string write_file(std::string_view path, long line_offset, long byte_offset,
                       long del_lines, long del_bytes,
                       std::string_view content, int *err);
std::string offload_tool_result(std::string_view res, int max_res,
                                std::vector<std::string> &tmps);
void cleanup_temps(std::vector<std::string> &tmps);

/* ------------------------------------------------------------------ */
/* session.cpp                                                         */
/* ------------------------------------------------------------------ */
void save_session(const Messages &msgs, std::string_view sid,
                  std::string *out_id, std::string *out_summary);
std::vector<Session> sessions_load();
std::unique_ptr<Messages> load_session(std::string_view sid, std::string *err);
std::unique_ptr<Session> find_project_session();
void autosave(const Messages &msgs);
std::unique_ptr<Messages> compact(Cfg &cfg, const Messages &msgs,
                                  std::string *summary, std::string *err,
                                  volatile int *interrupted);
std::string summary_of(const Messages &msgs);

/* ------------------------------------------------------------------ */
/* render.cpp — terminal markdown rendering.                           */
/* ------------------------------------------------------------------ */
void render_md_print(std::string_view text);
void render_md_line_print(std::string_view line, MdState &st);
void render_table_print(const std::vector<std::string> &lines);
bool is_table_line(std::string_view line);

/* ------------------------------------------------------------------ */
/* editor.cpp — GNU readline line editor + history (+ term helpers).   */
/* ------------------------------------------------------------------ */
void load_history();
void save_history();
void add_history(std::string_view s);
std::string read_line(std::string_view prompt, bool &ok);
std::string read_plain(std::string_view prompt, bool &ok);
int term_width();

#endif /* BANTAM_HPP */