/* linenoise.c -- guerrilla line editing library against the idea that a
 * line editing lib needs to be 20,000 lines of C code.
 *
 * You can find the latest source code at:
 * 
 *   http://github.com/antirez/linenoise
 *
 * Does a number of crazy assumptions that happen to be true in 99.9999% of
 * the 2010 UNIX computers around.
 *
 * ------------------------------------------------------------------------
 *
 * Copyright (c) 2010, Salvatore Sanfilippo <antirez at gmail dot com>
 * Copyright (c) 2010, Pieter Noordhuis <pcnoordhuis at gmail dot com>
 *
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *  *  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *  *  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * ------------------------------------------------------------------------
 *
 * References:
 * - http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
 * - http://www.3waylabs.com/nw/WWW/products/wizcon/vt220.html
 *
 * Todo list:
 * - Switch to gets() if $TERM is something we can't support.
 * - Filter bogus Ctrl+<char> combinations.
 * - Win32 support
 *
 * Bloat:
 * - History search like Ctrl+r in readline?
 *
 * List of escape sequences used by this program, we do everything just
 * with three sequences. In order to be so cheap we may have some
 * flickering effect with some slow terminal, but the lesser sequences
 * the more compatible.
 *
 * CHA (Cursor Horizontal Absolute)
 *    Sequence: ESC [ n G
 *    Effect: moves cursor to column n
 *
 * EL (Erase Line)
 *    Sequence: ESC [ n K
 *    Effect: if n is 0 or missing, clear from cursor to end of line
 *    Effect: if n is 1, clear from beginning of line to cursor
 *    Effect: if n is 2, clear entire line
 *
 * CUF (CUrsor Forward)
 *    Sequence: ESC [ n C
 *    Effect: moves cursor forward of n chars
 *
 * The following are used to clear the screen: ESC [ H ESC [ 2 J
 * This is actually composed of two sequences:
 *
 * cursorhome
 *    Sequence: ESC [ H
 *    Effect: moves the cursor to upper left corner
 *
 * ED2 (Clear entire screen)
 *    Sequence: ESC [ 2 J
 *    Effect: clear the whole screen
 * 
 */

#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include "linenoise.h"

#define LINENOISE_DEFAULT_HISTORY_MAX_LEN 100
#define LINENOISE_MAX_LINE 4096
static char *unsupported_term[] = {"dumb","cons25",NULL};
static linenoiseCompletionCallback *completionCallback = NULL;

static struct termios orig_termios; /* in order to restore at exit */
static int rawmode = 0; /* for atexit() function to check if restore is needed*/
static int atexit_registered = 0; /* register atexit just 1 time */
static int history_max_len = LINENOISE_DEFAULT_HISTORY_MAX_LEN;
static int history_len = 0;
char **history = NULL;

/* The linenoiseState structure represents the state during line editing.
 * We pass this state to functions implementing specific editing
 * functionalities. */
struct linenoiseState {
    int fd;             /* Terminal file descriptor. */
    char *buf;          /* Edited line buffer. */
    size_t buflen;      /* Edited line buffer size. */
    const char *prompt; /* Prompt to display. */
    size_t plen;        /* Prompt length. */
    size_t pos;         /* Current cursor position. */
    size_t len;         /* Current edited line length. */
    size_t cols;        /* Number of columns in terminal. */
    int history_index;  /* The history index we are currently editing. */
};

static void linenoiseAtExit(void);
int linenoiseHistoryAdd(const char *line);
static void refreshLine(struct linenoiseState *l);
static void refreshLineRaw(int fd, const char *prompt, char *buf, size_t len,
                           size_t pos, size_t cols);

/* ======================= Low level terminal handling ====================== */

/* Return true if the terminal name is in the list of terminals we know are
 * not able to understand basic escape sequences. */
static int isUnsupportedTerm(void) {
    char *term = getenv("TERM");
    int j;

    if (term == NULL) return 0;
    for (j = 0; unsupported_term[j]; j++)
        if (!strcasecmp(term,unsupported_term[j])) return 1;
    return 0;
}

/* Raw mode: 1960 magic shit. */
static int enableRawMode(int fd) {
    struct termios raw;

    if (!isatty(STDIN_FILENO)) goto fatal;
    if (!atexit_registered) {
        atexit(linenoiseAtExit);
        atexit_registered = 1;
    }
    if (tcgetattr(fd,&orig_termios) == -1) goto fatal;

    raw = orig_termios;  /* modify the original mode */
    /* input modes: no break, no CR to NL, no parity check, no strip char,
     * no start/stop output control. */
    raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
    /* output modes - disable post processing */
    raw.c_oflag &= ~(OPOST);
    /* control modes - set 8 bit chars */
    raw.c_cflag |= (CS8);
    /* local modes - choing off, canonical off, no extended functions,
     * no signal chars (^Z,^C) */
    raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
    /* control chars - set return condition: min number of bytes and timer.
     * We want read to return every single byte, without timeout. */
    raw.c_cc[VMIN] = 1; raw.c_cc[VTIME] = 0; /* 1 byte, no timer */

    /* put terminal in raw mode after flushing */
    if (tcsetattr(fd,TCSAFLUSH,&raw) < 0) goto fatal;
    rawmode = 1;
    return 0;

fatal:
    errno = ENOTTY;
    return -1;
}

static void disableRawMode(int fd) {
    /* Don't even check the return value as it's too late. */
    if (rawmode && tcsetattr(fd,TCSAFLUSH,&orig_termios) != -1)
        rawmode = 0;
}

/* Try to get the number of columns in the current terminal, or assume 80
 * if it fails. */
static int getColumns(void) {
    struct winsize ws;

    if (ioctl(1, TIOCGWINSZ, &ws) == -1) return 80;
    return ws.ws_col;
}

/* Clear the screen. Used to handle ctrl+l */
void linenoiseClearScreen(void) {
    if (write(STDIN_FILENO,"\x1b[H\x1b[2J",7) <= 0) {
        /* nothing to do, just to avoid warning. */
    }
}

/* Beep, used for completion when there is nothing to complete or when all
 * the choices were already shown. */
static void linenoiseBeep(void) {
    fprintf(stderr, "\x7");
    fflush(stderr);
}

/* ============================== Completion ================================ */

/* Free a list of completion option populated by linenoiseAddCompletion(). */
static void freeCompletions(linenoiseCompletions *lc) {
    size_t i;
    for (i = 0; i < lc->len; i++)
        free(lc->cvec[i]);
    if (lc->cvec != NULL)
        free(lc->cvec);
}

/* This is an helper function for linenoiseEdit() and is called when the
 * user types the <tab> key in order to complete the string currently in the
 * input.
 * 
 * The state of the editing is encapsulated into the pointed linenoiseState
 * structure as described in the structure definition. */
static int completeLine(struct linenoiseState *ls) {
    linenoiseCompletions lc = { 0, NULL };
    int nread, nwritten;
    char c = 0;

    completionCallback(ls->buf,&lc);
    if (lc.len == 0) {
        linenoiseBeep();
    } else {
        size_t stop = 0, i = 0;
        size_t clen;

        while(!stop) {
            /* Show completion or original buffer */
            if (i < lc.len) {
                clen = strlen(lc.cvec[i]);
                refreshLineRaw(ls->fd,ls->prompt,lc.cvec[i],clen,clen,ls->cols);
            } else {
                refreshLine(ls);
            }

            nread = read(ls->fd,&c,1);
            if (nread <= 0) {
                freeCompletions(&lc);
                return -1;
            }

            switch(c) {
                case 9: /* tab */
                    i = (i+1) % (lc.len+1);
                    if (i == lc.len) linenoiseBeep();
                    break;
                case 27: /* escape */
                    /* Re-show original buffer */
                    if (i < lc.len) refreshLine(ls);
                    stop = 1;
                    break;
                default:
                    /* Update buffer and return */
                    if (i < lc.len) {
                        nwritten = snprintf(ls->buf,ls->buflen,"%s",lc.cvec[i]);
                        ls->len = ls->pos = nwritten;
                    }
                    stop = 1;
                    break;
            }
        }
    }

    freeCompletions(&lc);
    return c; /* Return last read character */
}

/* Register a callback function to be called for tab-completion. */
void linenoiseSetCompletionCallback(linenoiseCompletionCallback *fn) {
    completionCallback = fn;
}

/* This function is used by the callback function registered by the user
 * in order to add completion options given the input string when the
 * user typed <tab>. See the example.c source code for a very easy to
 * understand example. */
void linenoiseAddCompletion(linenoiseCompletions *lc, char *str) {
    size_t len = strlen(str);
    char *copy = malloc(len+1);
    memcpy(copy,str,len+1);
    lc->cvec = realloc(lc->cvec,sizeof(char*)*(lc->len+1));
    lc->cvec[lc->len++] = copy;
}

/* =========================== Line editing ================================= */

/* Rewrite the currently edited line accordingly to the buffer content,
 * cursor position, and number of columns of the terminal. */
static void refreshLineRaw(int fd, const char *prompt, char *buf, size_t len,
                           size_t pos, size_t cols)
{
    char seq[64];
    size_t plen = strlen(prompt);
    
    while((plen+pos) >= cols) {
        buf++;
        len--;
        pos--;
    }
    while (plen+len > cols) {
        len--;
    }

    /* Cursor to left edge */
    snprintf(seq,64,"\x1b[0G");
    if (write(fd,seq,strlen(seq)) == -1) return;
    /* Write the prompt and the current buffer content */
    if (write(fd,prompt,strlen(prompt)) == -1) return;
    if (write(fd,buf,len) == -1) return;
    /* Erase to right */
    snprintf(seq,64,"\x1b[0K");
    if (write(fd,seq,strlen(seq)) == -1) return;
    /* Move cursor to original position. */
    snprintf(seq,64,"\x1b[0G\x1b[%dC", (int)(pos+plen));
    if (write(fd,seq,strlen(seq)) == -1) return;
}

/* A wrapper for refreshLineRaw() that take a state struct instead of the
 * single arguments. */
static void refreshLine(struct linenoiseState *l) {
    refreshLineRaw(l->fd, l->prompt, l->buf, l->len, l->pos, l->cols);
}

/* Insert the character 'c' at cursor current position.
 *
 * On error writing to the terminal -1 is returned, otherwise 0. */
int linenoiseEditInsert(struct linenoiseState *l, int c) {
    if (l->len < l->buflen) {
        if (l->len == l->pos) {
            l->buf[l->pos] = c;
            l->pos++;
            l->len++;
            l->buf[l->len] = '\0';
            if (l->plen+l->len < l->cols) {
                /* Avoid a full update of the line in the
                 * trivial case. */
                if (write(l->fd,&c,1) == -1) return -1;
            } else {
                refreshLine(l);
            }
        } else {
            memmove(l->buf+l->pos+1,l->buf+l->pos,l->len-l->pos);
            l->buf[l->pos] = c;
            l->len++;
            l->pos++;
            l->buf[l->len] = '\0';
            refreshLine(l);
        }
    }
    return 0;
}

/* Move cursor on the left. */
void linenoiseEditMoveLeft(struct linenoiseState *l) {
    if (l->pos > 0) {
        l->pos--;
        refreshLine(l);
    }
}

/* Move cursor on the right. */
void linenoiseEditMoveRight(struct linenoiseState *l) {
    if (l->pos != l->len) {
        l->pos++;
        refreshLine(l);
    }
}

/* Substitute the currently edited line with the next or previous history
 * entry as specified by 'dir'. */
#define LINENOISE_HISTORY_NEXT 0
#define LINENOISE_HISTORY_PREV 1
void linenoiseEditHistoryNext(struct linenoiseState *l, int dir) {
    if (history_len > 1) {
        /* Update the current history entry before to
         * overwrite it with the next one. */
        free(history[history_len - 1 - l->history_index]);
        history[history_len - 1 - l->history_index] = strdup(l->buf);
        /* Show the new entry */
        l->history_index += (dir == LINENOISE_HISTORY_PREV) ? 1 : -1;
        if (l->history_index < 0) {
            l->history_index = 0;
            return;
        } else if (l->history_index >= history_len) {
            l->history_index = history_len-1;
            return;
        }
        strncpy(l->buf,history[history_len - 1 - l->history_index],l->buflen);
        l->buf[l->buflen-1] = '\0';
        l->len = l->pos = strlen(l->buf);
        refreshLine(l);
    }
}

/* Delete the character at the right of the cursor without altering the cursor
 * position. Basically this is what happens with the "Delete" keyboard key. */
void linenoiseEditDelete(struct linenoiseState *l) {
    if (l->len > 0 && l->pos < l->len) {
        memmove(l->buf+l->pos,l->buf+l->pos+1,l->len-l->pos-1);
        l->len--;
        l->buf[l->len] = '\0';
        refreshLine(l);
    }
}

/* Backspace implementation. */
void linenoiseEditBackspace(struct linenoiseState *l) {
    if (l->pos > 0 && l->len > 0) {
        memmove(l->buf+l->pos-1,l->buf+l->pos,l->len-l->pos);
        l->pos--;
        l->len--;
        l->buf[l->len] = '\0';
        refreshLine(l);
    }
}

/* This function is the core of the line editing capability of linenoise.
 * It expects 'fd' to be already in "raw mode" so that every key pressed
 * will be returned ASAP to read().
 *
 * The resulting string is put into 'buf' when the user type enter, or
 * when ctrl+d is typed.
 *
 * The function returns the length of the current buffer. */
static int linenoiseEdit(int fd, char *buf, size_t buflen, const char *prompt)
{
    struct linenoiseState l;

    /* Populate the linenoise state that we pass to functions implementing
     * specific editing functionalities. */
    l.fd = fd;
    l.buf = buf;
    l.buflen = buflen;
    l.prompt = prompt;
    l.plen = strlen(prompt);
    l.pos = 0;
    l.len = 0;
    l.cols = getColumns();
    l.history_index = 0;
    size_t old_pos;
    size_t diff;

    /* Buffer starts empty. */
    buf[0] = '\0';
    buflen--; /* Make sure there is always space for the nulterm */

    /* The latest history entry is always our current buffer, that
     * initially is just an empty string. */
    linenoiseHistoryAdd("");
    
    if (write(fd,prompt,l.plen) == -1) return -1;
    while(1) {
        char c;
        int nread;
        char seq[2], seq2[2];

        nread = read(fd,&c,1);
        if (nread <= 0) return l.len;

        /* Only autocomplete when the callback is set. It returns < 0 when
         * there was an error reading from fd. Otherwise it will return the
         * character that should be handled next. */
        if (c == 9 && completionCallback != NULL) {
            c = completeLine(&l);
            /* Return on errors */
            if (c < 0) return l.len;
            /* Read next character when 0 */
            if (c == 0) continue;
        }

        switch(c) {
        case 13:    /* enter */
            history_len--;
            free(history[history_len]);
            return (int)l.len;
        case 3:     /* ctrl-c */
            errno = EAGAIN;
            return -1;
        case 127:   /* backspace */
        case 8:     /* ctrl-h */
            linenoiseEditBackspace(&l);
            break;
        case 4:     /* ctrl-d, remove char at right of cursor, or of the
                       line is empty, act as end-of-file. */
            if (l.len > 0) {
                linenoiseEditDelete(&l);
            } else {
                history_len--;
                free(history[history_len]);
                return -1;
            }
            break;
        case 20:    /* ctrl-t */
            if (l.pos > 0 && l.pos < l.len) {
                int aux = buf[l.pos-1];
                buf[l.pos-1] = buf[l.pos];
                buf[l.pos] = aux;
                if (l.pos != l.len-1) l.pos++;
                refreshLine(&l);
            }
            break;
        case 2:     /* ctrl-b */
            linenoiseEditMoveLeft(&l);
            break;
        case 6:     /* ctrl-f */
            linenoiseEditMoveRight(&l);
            break;
        case 16:    /* ctrl-p */
            linenoiseEditHistoryNext(&l, LINENOISE_HISTORY_PREV);
            break;
        case 14:    /* ctrl-n */
            linenoiseEditHistoryNext(&l, LINENOISE_HISTORY_NEXT);
            break;
        case 27:    /* escape sequence */
            if (read(fd,seq,2) == -1) break;
            if (seq[0] == 91 && seq[1] == 68) {
                linenoiseEditMoveLeft(&l);
            } else if (seq[0] == 91 && seq[1] == 67) {
                linenoiseEditMoveRight(&l);
            } else if (seq[0] == 91 && (seq[1] == 65 || seq[1] == 66)) {
                linenoiseEditHistoryNext(&l,
                    (seq[1] == 65) ? LINENOISE_HISTORY_PREV :
                                     LINENOISE_HISTORY_NEXT);
            } else if (seq[0] == 91 && seq[1] > 48 && seq[1] < 55) {
                /* extended escape */
                if (read(fd,seq2,2) == -1) break;
                if (seq[1] == 51 && seq2[0] == 126) {
                    linenoiseEditDelete(&l);
                }
            }
            break;
        default:
            if (linenoiseEditInsert(&l,c)) return -1;
            break;
        case 21: /* Ctrl+u, delete the whole line. */
            buf[0] = '\0';
            l.pos = l.len = 0;
            refreshLine(&l);
            break;
        case 11: /* Ctrl+k, delete from current to end of line. */
            buf[l.pos] = '\0';
            l.len = l.pos;
            refreshLine(&l);
            break;
        case 1: /* Ctrl+a, go to the start of the line */
            l.pos = 0;
            refreshLine(&l);
            break;
        case 5: /* ctrl+e, go to the end of the line */
            l.pos = l.len;
            refreshLine(&l);
            break;
        case 12: /* ctrl+l, clear screen */
            linenoiseClearScreen();
            refreshLine(&l);
            break;
        case 23: /* ctrl+w, delete previous word */
            old_pos = l.pos;
            while (l.pos > 0 && buf[l.pos-1] == ' ')
                l.pos--;
            while (l.pos > 0 && buf[l.pos-1] != ' ')
                l.pos--;
            diff = old_pos - l.pos;
            memmove(&buf[l.pos], &buf[old_pos], l.len-old_pos+1);
            l.len -= diff;
            refreshLine(&l);
            break;
        }
    }
    return l.len;
}

/* This function calls the line editing function linenoiseEdit() using
 * the STDIN file descriptor set in raw mode. */
static int linenoiseRaw(char *buf, size_t buflen, const char *prompt) {
    int fd = STDIN_FILENO;
    int count;

    if (buflen == 0) {
        errno = EINVAL;
        return -1;
    }
    if (!isatty(STDIN_FILENO)) {
        if (fgets(buf, buflen, stdin) == NULL) return -1;
        count = strlen(buf);
        if (count && buf[count-1] == '\n') {
            count--;
            buf[count] = '\0';
        }
    } else {
        if (enableRawMode(fd) == -1) return -1;
        count = linenoiseEdit(fd, buf, buflen, prompt);
        disableRawMode(fd);
        printf("\n");
    }
    return count;
}

/* The high level function that is the main API of the linenoise library.
 * This function checks if the terminal has basic capabilities, just checking
 * for a blacklist of stupid terminals, and later either calls the line
 * editing function or uses dummy fgets() so that you will be able to type
 * something even in the most desperate of the conditions. */
char *linenoise(const char *prompt) {
    char buf[LINENOISE_MAX_LINE];
    int count;

    if (isUnsupportedTerm()) {
        size_t len;

        printf("%s",prompt);
        fflush(stdout);
        if (fgets(buf,LINENOISE_MAX_LINE,stdin) == NULL) return NULL;
        len = strlen(buf);
        while(len && (buf[len-1] == '\n' || buf[len-1] == '\r')) {
            len--;
            buf[len] = '\0';
        }
        return strdup(buf);
    } else {
        count = linenoiseRaw(buf,LINENOISE_MAX_LINE,prompt);
        if (count == -1) return NULL;
        return strdup(buf);
    }
}

/* ================================ History ================================= */

/* Free the history, but does not reset it. Only used when we have to
 * exit() to avoid memory leaks are reported by valgrind & co. */
static void freeHistory(void) {
    if (history) {
        int j;

        for (j = 0; j < history_len; j++)
            free(history[j]);
        free(history);
    }
}

/* At exit we'll try to fix the terminal to the initial conditions. */
static void linenoiseAtExit(void) {
    disableRawMode(STDIN_FILENO);
    freeHistory();
}

/* Using a circular buffer is smarter, but a bit more complex to handle. */
int linenoiseHistoryAdd(const char *line) {
    char *linecopy;

    if (history_max_len == 0) return 0;
    if (history == NULL) {
        history = malloc(sizeof(char*)*history_max_len);
        if (history == NULL) return 0;
        memset(history,0,(sizeof(char*)*history_max_len));
    }
    linecopy = strdup(line);
    if (!linecopy) return 0;
    if (history_len == history_max_len) {
        free(history[0]);
        memmove(history,history+1,sizeof(char*)*(history_max_len-1));
        history_len--;
    }
    history[history_len] = linecopy;
    history_len++;
    return 1;
}

/* Set the maximum length for the history. This function can be called even
 * if there is already some history, the function will make sure to retain
 * just the latest 'len' elements if the new history length value is smaller
 * than the amount of items already inside the history. */
int linenoiseHistorySetMaxLen(int len) {
    char **new;

    if (len < 1) return 0;
    if (history) {
        int tocopy = history_len;

        new = malloc(sizeof(char*)*len);
        if (new == NULL) return 0;
        if (len < tocopy) tocopy = len;
        memcpy(new,history+(history_max_len-tocopy), sizeof(char*)*tocopy);
        free(history);
        history = new;
    }
    history_max_len = len;
    if (history_len > history_max_len)
        history_len = history_max_len;
    return 1;
}

/* Save the history in the specified file. On success 0 is returned
 * otherwise -1 is returned. */
int linenoiseHistorySave(char *filename) {
    FILE *fp = fopen(filename,"w");
    int j;
    
    if (fp == NULL) return -1;
    for (j = 0; j < history_len; j++)
        fprintf(fp,"%s\n",history[j]);
    fclose(fp);
    return 0;
}

/* Load the history from the specified file. If the file does not exist
 * zero is returned and no operation is performed.
 *
 * If the file exists and the operation succeeded 0 is returned, otherwise
 * on error -1 is returned. */
int linenoiseHistoryLoad(char *filename) {
    FILE *fp = fopen(filename,"r");
    char buf[LINENOISE_MAX_LINE];
    
    if (fp == NULL) return -1;

    while (fgets(buf,LINENOISE_MAX_LINE,fp) != NULL) {
        char *p;
        
        p = strchr(buf,'\r');
        if (!p) p = strchr(buf,'\n');
        if (p) *p = '\0';
        linenoiseHistoryAdd(buf);
    }
    fclose(fp);
    return 0;
}