#include <assert.h>
#include <stdint.h>
#include <string.h>

#include "nvim/memory.h"
#include "nvim/tui/termkey/driver-csi.h"
#include "nvim/tui/termkey/termkey-internal.h"
#include "nvim/tui/termkey/termkey_defs.h"

#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "tui/termkey/driver-csi.c.generated.h"
#endif

// There are 64 codes 0x40 - 0x7F
static int keyinfo_initialised = 0;
static struct keyinfo ss3s[64];
static char ss3_kpalts[64];

typedef TermKeyResult CsiHandler(TermKey *tk, TermKeyKey *key, int cmd, TermKeyCsiParam *params,
                                 int nparams);
static CsiHandler *csi_handlers[64];

// Handler for CSI/SS3 cmd keys

static struct keyinfo csi_ss3s[64];

static TermKeyResult handle_csi_ss3_full(TermKey *tk, TermKeyKey *key, int cmd,
                                         TermKeyCsiParam *params, int nparams)
{
  TermKeyResult result = TERMKEY_RES_KEY;

  if (nparams > 1 && params[1].param != NULL) {
    int arg = 0;
    int subparam = 0;
    size_t nsubparams = 1;
    result = termkey_interpret_csi_param(params[1], &arg, &subparam, &nsubparams);
    if (result != TERMKEY_RES_KEY) {
      return result;
    }

    if (nsubparams > 0) {
      key->event = parse_key_event(subparam);
      if (key->event == TERMKEY_EVENT_UNKNOWN) {
        return TERMKEY_RES_NONE;
      }
    }

    key->modifiers = arg - 1;
  } else {
    key->modifiers = 0;
  }

  key->type = csi_ss3s[cmd - 0x40].type;
  key->code.sym = csi_ss3s[cmd - 0x40].sym;
  key->modifiers &= ~(csi_ss3s[cmd - 0x40].modifier_mask);
  key->modifiers |= csi_ss3s[cmd - 0x40].modifier_set;

  if (key->code.sym == TERMKEY_SYM_UNKNOWN) {
    result = TERMKEY_RES_NONE;
  }

  return result;
}

static void register_csi_ss3_full(TermKeyType type, TermKeySym sym, int modifier_set,
                                  int modifier_mask, unsigned char cmd)
{
  if (cmd < 0x40 || cmd >= 0x80) {
    return;
  }

  csi_ss3s[cmd - 0x40].type = type;
  csi_ss3s[cmd - 0x40].sym = sym;
  csi_ss3s[cmd - 0x40].modifier_set = modifier_set;
  csi_ss3s[cmd - 0x40].modifier_mask = modifier_mask;

  csi_handlers[cmd - 0x40] = &handle_csi_ss3_full;
}

static void register_csi_ss3(TermKeyType type, TermKeySym sym, unsigned char cmd)
{
  register_csi_ss3_full(type, sym, 0, 0, cmd);
}

/// Handler for SS3 keys with kpad alternate representations
static void register_ss3kpalt(TermKeyType type, TermKeySym sym, unsigned char cmd, char kpalt)
{
  if (cmd < 0x40 || cmd >= 0x80) {
    return;
  }

  ss3s[cmd - 0x40].type = type;
  ss3s[cmd - 0x40].sym = sym;
  ss3s[cmd - 0x40].modifier_set = 0;
  ss3s[cmd - 0x40].modifier_mask = 0;
  ss3_kpalts[cmd - 0x40] = kpalt;
}

// Handler for CSI number ~ function keys

#define NCSIFUNCS 35  // This value must be increased if more CSI function keys are added
static struct keyinfo csifuncs[NCSIFUNCS];

static TermKeyResult handle_csifunc(TermKey *tk, TermKeyKey *key, int cmd, TermKeyCsiParam *params,
                                    int nparams)
{
  if (nparams == 0) {
    return TERMKEY_RES_NONE;
  }

  TermKeyResult result = TERMKEY_RES_KEY;
  int args[3];

  if (nparams > 1 && params[1].param != NULL) {
    int subparam = 0;
    size_t nsubparams = 1;
    result = termkey_interpret_csi_param(params[1], &args[1], &subparam, &nsubparams);
    if (result != TERMKEY_RES_KEY) {
      return result;
    }

    if (nsubparams > 0) {
      key->event = parse_key_event(subparam);
      if (key->event == TERMKEY_EVENT_UNKNOWN) {
        return TERMKEY_RES_NONE;
      }
    }

    key->modifiers = args[1] - 1;
  } else {
    key->modifiers = 0;
  }

  key->type = TERMKEY_TYPE_KEYSYM;

  result = termkey_interpret_csi_param(params[0], &args[0], NULL, NULL);
  if (result != TERMKEY_RES_KEY) {
    return result;
  }

  if (args[0] == 27 && nparams > 2 && params[2].param != NULL) {
    result = termkey_interpret_csi_param(params[2], &args[2], NULL, NULL);
    if (result != TERMKEY_RES_KEY) {
      return result;
    }

    int mod = key->modifiers;
    (*tk->method.emit_codepoint)(tk, args[2], key);
    key->modifiers |= mod;
  } else if (args[0] >= 0 && args[0] < NCSIFUNCS) {
    key->type = csifuncs[args[0]].type;
    key->code.sym = csifuncs[args[0]].sym;
    key->modifiers &= ~(csifuncs[args[0]].modifier_mask);
    key->modifiers |= csifuncs[args[0]].modifier_set;
  } else {
    key->code.sym = TERMKEY_SYM_UNKNOWN;
  }

  if (key->code.sym == TERMKEY_SYM_UNKNOWN) {
#ifdef DEBUG
    fprintf(stderr, "CSI: Unknown function key %ld\n", arg[0]);
#endif
    result = TERMKEY_RES_NONE;
  }

  return result;
}

static void register_csifunc(TermKeyType type, TermKeySym sym, int number)
{
  if (number >= NCSIFUNCS) {
    return;
  }

  csifuncs[number].type = type;
  csifuncs[number].sym = sym;
  csifuncs[number].modifier_set = 0;
  csifuncs[number].modifier_mask = 0;

  csi_handlers['~' - 0x40] = &handle_csifunc;
}

/// Handler for CSI u extended Unicode keys
static TermKeyResult handle_csi_u(TermKey *tk, TermKeyKey *key, int cmd, TermKeyCsiParam *params,
                                  int nparams)
{
  switch (cmd) {
  case 'u': {
    int args[2];
    if (nparams > 1 && params[1].param != NULL) {
      int subparam = 0;
      size_t nsubparams = 1;
      if (termkey_interpret_csi_param(params[1], &args[1], &subparam,
                                      &nsubparams) != TERMKEY_RES_KEY) {
        return TERMKEY_RES_ERROR;
      }

      if (nsubparams > 0) {
        key->event = parse_key_event(subparam);
        if (key->event == TERMKEY_EVENT_UNKNOWN) {
          return TERMKEY_RES_NONE;
        }
      }

      key->modifiers = args[1] - 1;
    } else {
      key->modifiers = 0;
    }

    if (termkey_interpret_csi_param(params[0], &args[0], NULL, NULL) != TERMKEY_RES_KEY) {
      return TERMKEY_RES_ERROR;
    }

    int mod = key->modifiers;
    key->type = TERMKEY_TYPE_KEYSYM;
    (*tk->method.emit_codepoint)(tk, args[0], key);
    key->modifiers |= mod;

    return TERMKEY_RES_KEY;
  }
  default:
    return TERMKEY_RES_NONE;
  }
}

/// Handler for CSI M / CSI m mouse events in SGR and rxvt encodings
/// Note: This does not handle X10 encoding
static TermKeyResult handle_csi_m(TermKey *tk, TermKeyKey *key, int cmd, TermKeyCsiParam *params,
                                  int nparams)
{
  int initial = cmd >> 8;
  cmd &= 0xff;

  switch (cmd) {
  case 'M':
  case 'm':
    break;
  default:
    return TERMKEY_RES_NONE;
  }

  if (nparams < 3) {
    return TERMKEY_RES_NONE;
  }

  int args[3];
  for (size_t i = 0; i < 3; i++) {
    if (termkey_interpret_csi_param(params[i], &args[i], NULL, NULL) != TERMKEY_RES_KEY) {
      return TERMKEY_RES_ERROR;
    }
  }

  if (!initial) {  // rxvt protocol
    key->type = TERMKEY_TYPE_MOUSE;
    key->code.mouse[0] = (char)args[0];

    key->modifiers = (key->code.mouse[0] & 0x1c) >> 2;
    key->code.mouse[0] &= ~0x1c;

    termkey_key_set_linecol(key, args[1], args[2]);

    return TERMKEY_RES_KEY;
  }

  if (initial == '<') {  // SGR protocol
    key->type = TERMKEY_TYPE_MOUSE;
    key->code.mouse[0] = (char)args[0];

    key->modifiers = (key->code.mouse[0] & 0x1c) >> 2;
    key->code.mouse[0] &= ~0x1c;

    termkey_key_set_linecol(key, args[1], args[2]);

    if (cmd == 'm') {  // release
      key->code.mouse[3] |= 0x80;
    }

    return TERMKEY_RES_KEY;
  }

  return TERMKEY_RES_NONE;
}

TermKeyResult termkey_interpret_mouse(TermKey *tk, const TermKeyKey *key, TermKeyMouseEvent *event,
                                      int *button, int *line, int *col)
{
  if (key->type != TERMKEY_TYPE_MOUSE) {
    return TERMKEY_RES_NONE;
  }

  if (button) {
    *button = 0;
  }

  termkey_key_get_linecol(key, line, col);

  if (!event) {
    return TERMKEY_RES_KEY;
  }

  int btn = 0;

  int code = (unsigned char)key->code.mouse[0];

  int drag = code & 0x20;

  code &= ~0x3c;

  switch (code) {
  case 0:
  case 1:
  case 2:
    *event = drag ? TERMKEY_MOUSE_DRAG : TERMKEY_MOUSE_PRESS;
    btn = code + 1;
    break;

  case 3:
    *event = TERMKEY_MOUSE_RELEASE;
    // no button hint
    break;

  case 64:
  case 65:
  case 66:
  case 67:
    *event = drag ? TERMKEY_MOUSE_DRAG : TERMKEY_MOUSE_PRESS;
    btn = code + 4 - 64;
    break;

  case 128:
  case 129:
    *event = drag ? TERMKEY_MOUSE_DRAG : TERMKEY_MOUSE_PRESS;
    btn = code + 8 - 128;
    break;

  default:
    *event = TERMKEY_MOUSE_UNKNOWN;
  }

  if (button) {
    *button = btn;
  }

  if (key->code.mouse[3] & 0x80) {
    *event = TERMKEY_MOUSE_RELEASE;
  }

  return TERMKEY_RES_KEY;
}

/// Handler for CSI ? R position reports
/// A plain CSI R with no arguments is probably actually <F3>
static TermKeyResult handle_csi_R(TermKey *tk, TermKeyKey *key, int cmd, TermKeyCsiParam *params,
                                  int nparams)
{
  switch (cmd) {
  case 'R'|'?' << 8:
      if (nparams < 2) {
      return TERMKEY_RES_NONE;
      }

      int args[2];
    if (termkey_interpret_csi_param(params[0], &args[0], NULL, NULL) != TERMKEY_RES_KEY) {
      return TERMKEY_RES_ERROR;
    }

    if (termkey_interpret_csi_param(params[1], &args[1], NULL, NULL) != TERMKEY_RES_KEY) {
      return TERMKEY_RES_ERROR;
    }

    key->type = TERMKEY_TYPE_POSITION;
    termkey_key_set_linecol(key, args[1], args[0]);
    return TERMKEY_RES_KEY;

  default:
    return handle_csi_ss3_full(tk, key, cmd, params, nparams);
  }
}

TermKeyResult termkey_interpret_position(TermKey *tk, const TermKeyKey *key, int *line, int *col)
{
  if (key->type != TERMKEY_TYPE_POSITION) {
    return TERMKEY_RES_NONE;
  }

  termkey_key_get_linecol(key, line, col);

  return TERMKEY_RES_KEY;
}

/// Handler for CSI $y mode status reports
static TermKeyResult handle_csi_y(TermKey *tk, TermKeyKey *key, int cmd, TermKeyCsiParam *params,
                                  int nparams)
{
  switch (cmd) {
  case 'y'|'$' << 16:
      case 'y'|'$' << 16 | '?' << 8:
      if (nparams < 2) {
      return TERMKEY_RES_NONE;
      }

      int args[2];
    if (termkey_interpret_csi_param(params[0], &args[0], NULL, NULL) != TERMKEY_RES_KEY) {
      return TERMKEY_RES_ERROR;
    }

    if (termkey_interpret_csi_param(params[1], &args[1], NULL, NULL) != TERMKEY_RES_KEY) {
      return TERMKEY_RES_ERROR;
    }

    key->type = TERMKEY_TYPE_MODEREPORT;
    key->code.mouse[0] = (char)(cmd >> 8);
    key->code.mouse[1] = (char)(args[0] >> 8);
    key->code.mouse[2] = (char)(args[0] & 0xff);
    key->code.mouse[3] = (char)args[1];
    return TERMKEY_RES_KEY;

  default:
    return TERMKEY_RES_NONE;
  }
}

TermKeyResult termkey_interpret_modereport(TermKey *tk, const TermKeyKey *key, int *initial,
                                           int *mode, int *value)
{
  if (key->type != TERMKEY_TYPE_MODEREPORT) {
    return TERMKEY_RES_NONE;
  }

  if (initial) {
    *initial = (unsigned char)key->code.mouse[0];
  }

  if (mode) {
    *mode = ((uint8_t)key->code.mouse[1] << 8) | (uint8_t)key->code.mouse[2];
  }

  if (value) {
    *value = (unsigned char)key->code.mouse[3];
  }

  return TERMKEY_RES_KEY;
}

#define CHARAT(i) (tk->buffer[tk->buffstart + (i)])

static TermKeyEvent parse_key_event(int n)
{
  switch (n) {
  case 1:
    return TERMKEY_EVENT_PRESS;
  case 2:
    return TERMKEY_EVENT_REPEAT;
  case 3:
    return TERMKEY_EVENT_RELEASE;
  default:
    return TERMKEY_EVENT_UNKNOWN;
  }
}

static TermKeyResult parse_csi(TermKey *tk, size_t introlen, size_t *csi_len,
                               TermKeyCsiParam params[], size_t *nargs, unsigned *commandp)
{
  size_t csi_end = introlen;

  while (csi_end < tk->buffcount) {
    if (CHARAT(csi_end) >= 0x40 && CHARAT(csi_end) < 0x80) {
      break;
    }
    csi_end++;
  }

  if (csi_end >= tk->buffcount) {
    return TERMKEY_RES_AGAIN;
  }

  unsigned char cmd = CHARAT(csi_end);
  *commandp = cmd;

  char present = 0;
  int argi = 0;

  size_t p = introlen;

  // See if there is an initial byte
  if (CHARAT(p) >= '<' && CHARAT(p) <= '?') {
    *commandp |= (unsigned)(CHARAT(p) << 8);
    p++;
  }

  // Now attempt to parse out up number;number;... separated values
  while (p < csi_end) {
    unsigned char c = CHARAT(p);

    if (c >= '0' && c < ';') {
      if (!present) {
        params[argi].param = &CHARAT(p);
        present = 1;
      }
    } else if (c == ';') {
      if (!present) {
        params[argi].param = NULL;
        params[argi].length = 0;
      } else {
        params[argi].length = (size_t)(&CHARAT(p) - params[argi].param);
      }
      present = 0;
      argi++;

      if (argi > 16) {
        break;
      }
    } else if (c >= 0x20 && c <= 0x2f) {
      *commandp |= (unsigned)(c << 16);
      break;
    }

    p++;
  }

  if (present) {
    params[argi].length = (size_t)(&CHARAT(p) - params[argi].param);
    argi++;
  }

  *nargs = (size_t)argi;
  *csi_len = csi_end + 1;

  return TERMKEY_RES_KEY;
}

TermKeyResult termkey_interpret_csi(TermKey *tk, const TermKeyKey *key, TermKeyCsiParam params[],
                                    size_t *nparams, unsigned *cmd)
{
  size_t dummy;

  if (tk->hightide == 0) {
    return TERMKEY_RES_NONE;
  }
  if (key->type != TERMKEY_TYPE_UNKNOWN_CSI) {
    return TERMKEY_RES_NONE;
  }

  return parse_csi(tk, 0, &dummy, params, nparams, cmd);
}

TermKeyResult termkey_interpret_csi_param(TermKeyCsiParam param, int *paramp, int subparams[],
                                          size_t *nsubparams)
{
  if (paramp == NULL) {
    return TERMKEY_RES_ERROR;
  }

  if (param.param == NULL) {
    *paramp = -1;
    if (nsubparams) {
      *nsubparams = 0;
    }
    return TERMKEY_RES_KEY;
  }

  int arg = 0;
  size_t i = 0;
  size_t capacity = nsubparams ? *nsubparams : 0;
  size_t length = 0;
  for (; i < param.length && length <= capacity; i++) {
    unsigned char c = param.param[i];
    if (c == ':') {
      if (length == 0) {
        *paramp = arg;
      } else if (subparams != NULL) {
        subparams[length - 1] = arg;
      }

      arg = 0;
      length++;
      continue;
    }

    assert(c >= '0' && c <= '9');
    arg = (10 * arg) + (c - '0');
  }

  if (length == 0) {
    *paramp = arg;
  } else if (subparams != NULL) {
    subparams[length - 1] = arg;
  }

  if (nsubparams) {
    *nsubparams = length;
  }

  return TERMKEY_RES_KEY;
}

static int register_keys(void)
{
  int i;

  for (i = 0; i < 64; i++) {
    csi_ss3s[i].sym = TERMKEY_SYM_UNKNOWN;
    ss3s[i].sym = TERMKEY_SYM_UNKNOWN;
    ss3_kpalts[i] = 0;
  }

  for (i = 0; i < NCSIFUNCS; i++) {
    csifuncs[i].sym = TERMKEY_SYM_UNKNOWN;
  }

  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_UP,    'A');
  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_DOWN,  'B');
  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_RIGHT, 'C');
  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_LEFT,  'D');
  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_BEGIN, 'E');
  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_END,   'F');
  register_csi_ss3(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_HOME,  'H');
  register_csi_ss3(TERMKEY_TYPE_FUNCTION, 1, 'P');
  register_csi_ss3(TERMKEY_TYPE_FUNCTION, 2, 'Q');
  register_csi_ss3(TERMKEY_TYPE_FUNCTION, 3, 'R');
  register_csi_ss3(TERMKEY_TYPE_FUNCTION, 4, 'S');

  register_csi_ss3_full(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_TAB, TERMKEY_KEYMOD_SHIFT,
                        TERMKEY_KEYMOD_SHIFT, 'Z');

  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPENTER,  'M', 0);
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPEQUALS, 'X', '=');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPMULT,   'j', '*');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPPLUS,   'k', '+');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPCOMMA,  'l', ',');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPMINUS,  'm', '-');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPPERIOD, 'n', '.');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KPDIV,    'o', '/');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP0,      'p', '0');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP1,      'q', '1');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP2,      'r', '2');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP3,      's', '3');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP4,      't', '4');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP5,      'u', '5');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP6,      'v', '6');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP7,      'w', '7');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP8,      'x', '8');
  register_ss3kpalt(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_KP9,      'y', '9');

  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_FIND,      1);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_INSERT,    2);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_DELETE,    3);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_SELECT,    4);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_PAGEUP,    5);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_PAGEDOWN,  6);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_HOME,      7);
  register_csifunc(TERMKEY_TYPE_KEYSYM, TERMKEY_SYM_END,       8);

  register_csifunc(TERMKEY_TYPE_FUNCTION, 1,  11);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 2,  12);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 3,  13);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 4,  14);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 5,  15);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 6,  17);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 7,  18);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 8,  19);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 9,  20);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 10, 21);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 11, 23);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 12, 24);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 13, 25);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 14, 26);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 15, 28);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 16, 29);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 17, 31);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 18, 32);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 19, 33);
  register_csifunc(TERMKEY_TYPE_FUNCTION, 20, 34);

  csi_handlers['u' - 0x40] = &handle_csi_u;

  csi_handlers['M' - 0x40] = &handle_csi_m;
  csi_handlers['m' - 0x40] = &handle_csi_m;

  csi_handlers['R' - 0x40] = &handle_csi_R;

  csi_handlers['y' - 0x40] = &handle_csi_y;

  keyinfo_initialised = 1;
  return 1;
}

void *new_driver_csi(TermKey *tk, const char *term)
{
  if (!keyinfo_initialised) {
    if (!register_keys()) {
      return NULL;
    }
  }

  TermKeyCsi *csi = xmalloc(sizeof *csi);

  csi->tk = tk;
  csi->saved_string_id = 0;
  csi->saved_string = NULL;

  return csi;
}

void free_driver_csi(void *info)
{
  TermKeyCsi *csi = info;

  if (csi->saved_string) {
    xfree(csi->saved_string);
  }

  xfree(csi);
}

static TermKeyResult peekkey_csi_csi(TermKey *tk, TermKeyCsi *csi, size_t introlen, TermKeyKey *key,
                                     int force, size_t *nbytep)
{
  size_t csi_len;
  size_t nparams = 16;
  TermKeyCsiParam params[16];
  unsigned cmd;

  TermKeyResult ret = parse_csi(tk, introlen, &csi_len, params, &nparams, &cmd);

  if (ret == TERMKEY_RES_AGAIN) {
    if (!force) {
      return TERMKEY_RES_AGAIN;
    }

    (*tk->method.emit_codepoint)(tk, '[', key);
    key->modifiers |= TERMKEY_KEYMOD_ALT;
    *nbytep = introlen;
    return TERMKEY_RES_KEY;
  }

  if (cmd == 'M' && nparams < 3) {  // Mouse in X10 encoding consumes the next 3 bytes also
    tk->buffstart += csi_len;
    tk->buffcount -= csi_len;

    TermKeyResult mouse_result = (*tk->method.peekkey_mouse)(tk, key, nbytep);

    tk->buffstart -= csi_len;
    tk->buffcount += csi_len;

    if (mouse_result == TERMKEY_RES_KEY) {
      *nbytep += csi_len;
    }

    return mouse_result;
  }

  TermKeyResult result = TERMKEY_RES_NONE;

  // We know from the logic above that cmd must be >= 0x40 and < 0x80
  if (csi_handlers[(cmd & 0xff) - 0x40]) {
    result = (*csi_handlers[(cmd & 0xff) - 0x40])(tk, key, (int)cmd, params, (int)nparams);
  }

  if (result == TERMKEY_RES_NONE) {
#ifdef DEBUG
    switch (args) {
    case 0:
      fprintf(stderr, "CSI: Unknown cmd=%c\n", (char)cmd);
      break;
    case 1:
      fprintf(stderr, "CSI: Unknown arg1=%ld cmd=%c\n", arg[0], (char)cmd);
      break;
    case 2:
      fprintf(stderr, "CSI: Unknown arg1=%ld arg2=%ld cmd=%c\n", arg[0], arg[1], (char)cmd);
      break;
    case 3:
      fprintf(stderr, "CSI: Unknown arg1=%ld arg2=%ld arg3=%ld cmd=%c\n", arg[0], arg[1], arg[2],
              (char)cmd);
      break;
    default:
      fprintf(stderr, "CSI: Unknown arg1=%ld arg2=%ld arg3=%ld ... args=%d cmd=%c\n", arg[0],
              arg[1], arg[2], args, (char)cmd);
      break;
    }
#endif
    key->type = TERMKEY_TYPE_UNKNOWN_CSI;
    key->code.number = (int)cmd;
    key->modifiers = 0;

    tk->hightide = csi_len - introlen;
    *nbytep = introlen;  // Do not yet eat the data bytes
    return TERMKEY_RES_KEY;
  }

  *nbytep = csi_len;
  return result;
}

static TermKeyResult peekkey_ss3(TermKey *tk, TermKeyCsi *csi, size_t introlen, TermKeyKey *key,
                                 int force, size_t *nbytep)
{
  if (tk->buffcount < introlen + 1) {
    if (!force) {
      return TERMKEY_RES_AGAIN;
    }

    (*tk->method.emit_codepoint)(tk, 'O', key);
    key->modifiers |= TERMKEY_KEYMOD_ALT;
    *nbytep = tk->buffcount;
    return TERMKEY_RES_KEY;
  }

  unsigned char cmd = CHARAT(introlen);

  if (cmd < 0x40 || cmd >= 0x80) {
    return TERMKEY_RES_NONE;
  }

  key->type = csi_ss3s[cmd - 0x40].type;
  key->code.sym = csi_ss3s[cmd - 0x40].sym;
  key->modifiers = csi_ss3s[cmd - 0x40].modifier_set;

  if (key->code.sym == TERMKEY_SYM_UNKNOWN) {
    if (tk->flags & TERMKEY_FLAG_CONVERTKP && ss3_kpalts[cmd - 0x40]) {
      key->type = TERMKEY_TYPE_UNICODE;
      key->code.codepoint = (unsigned char)ss3_kpalts[cmd - 0x40];
      key->modifiers = 0;

      key->utf8[0] = (char)key->code.codepoint;
      key->utf8[1] = 0;
    } else {
      key->type = ss3s[cmd - 0x40].type;
      key->code.sym = ss3s[cmd - 0x40].sym;
      key->modifiers = ss3s[cmd - 0x40].modifier_set;
    }
  }

  if (key->code.sym == TERMKEY_SYM_UNKNOWN) {
#ifdef DEBUG
    fprintf(stderr, "CSI: Unknown SS3 %c (0x%02x)\n", (char)cmd, cmd);
#endif
    return TERMKEY_RES_NONE;
  }

  *nbytep = introlen + 1;

  return TERMKEY_RES_KEY;
}

static TermKeyResult peekkey_ctrlstring(TermKey *tk, TermKeyCsi *csi, size_t introlen,
                                        TermKeyKey *key, int force, size_t *nbytep)
{
  size_t str_end = introlen;

  while (str_end < tk->buffcount) {
    if (CHARAT(str_end) == 0x07) {  // BEL
      break;
    }
    if (CHARAT(str_end) == 0x9c) {  // ST
      break;
    }
    if (CHARAT(str_end) == 0x1b
        && (str_end + 1) < tk->buffcount
        && CHARAT(str_end + 1) == 0x5c) {  // ESC-prefixed ST
      break;
    }

    str_end++;
  }

  if (str_end >= tk->buffcount) {
    return TERMKEY_RES_AGAIN;
  }

#ifdef DEBUG
  fprintf(stderr, "Found a control string: %*s",
          str_end - introlen, tk->buffer + tk->buffstart + introlen);
#endif

  *nbytep = str_end + 1;
  if (CHARAT(str_end) == 0x1b) {
    (*nbytep)++;
  }

  if (csi->saved_string) {
    xfree(csi->saved_string);
  }

  size_t len = str_end - introlen;

  csi->saved_string_id++;
  csi->saved_string = xmalloc(len + 1);

  strncpy(csi->saved_string, (char *)tk->buffer + tk->buffstart + introlen, len);  // NOLINT(runtime/printf)
  csi->saved_string[len] = 0;

  key->type = (CHARAT(introlen - 1) & 0x1f) == 0x10
              ? TERMKEY_TYPE_DCS : TERMKEY_TYPE_OSC;
  key->code.number = csi->saved_string_id;
  key->modifiers = 0;

  return TERMKEY_RES_KEY;
}

TermKeyResult peekkey_csi(TermKey *tk, void *info, TermKeyKey *key, int force, size_t *nbytep)
{
  if (tk->buffcount == 0) {
    return tk->is_closed ? TERMKEY_RES_EOF : TERMKEY_RES_NONE;
  }

  TermKeyCsi *csi = info;

  switch (CHARAT(0)) {
  case 0x1b:
    if (tk->buffcount < 2) {
      return TERMKEY_RES_NONE;
    }

    switch (CHARAT(1)) {
    case 0x4f:  // ESC-prefixed SS3
      return peekkey_ss3(tk, csi, 2, key, force, nbytep);

    case 0x50:  // ESC-prefixed DCS
    case 0x5d:  // ESC-prefixed OSC
      return peekkey_ctrlstring(tk, csi, 2, key, force, nbytep);

    case 0x5b:  // ESC-prefixed CSI
      return peekkey_csi_csi(tk, csi, 2, key, force, nbytep);
    }

    return TERMKEY_RES_NONE;

  case 0x8f:  // SS3
    return peekkey_ss3(tk, csi, 1, key, force, nbytep);

  case 0x90:  // DCS
  case 0x9d:  // OSC
    return peekkey_ctrlstring(tk, csi, 1, key, force, nbytep);

  case 0x9b:  // CSI
    return peekkey_csi_csi(tk, csi, 1, key, force, nbytep);
  }

  return TERMKEY_RES_NONE;
}