//----------------------------------------------------------------------------//
//                                OS on Kaleid                                //
//                                                                            //
//  Desc:       Kernel shell                                                  //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2021 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <io/vga.h>
#include <io/keyb.h>
#include <io/spkr.h>
#include <libbuf.h>
#include <sh/argv.h>
#include <sh/shell.h>
#include <po/shtdwn.h>
#include <io/cursor.h>

int shargc = 0;
char **shargv = 0;
int shcol = VGA_COLOR_LIGHT_GREY;

char *shprompt = "shell> ";
size_t shpromptlen = 7;

static char *argvbuf = 0;

void ExecuteCommand(char *cmdbuf, Command_t *cmdtable)
{
    error_t rc;
    Command_t *cmd;
    bool found = false;
    
    if (!cmdbuf || !*cmdbuf)
        return;

    memzero(*shargv, ARG_MAX);
    rc = ShCmdLineToArgVec(cmdbuf, &shargc, argvbuf);
    if (rc) KeStartPanic("Shell: Couldn't parse command line: %d", rc);

    for (cmd = cmdtable; cmd->name != NULL; cmd++) {
        if (!strcmp(cmd->name, shargv[0])) {
            cmd->func(shargc, shargv, cmdbuf);
            found = true;
            break;
        }
    }
    
    assert(shargv[0] == argvbuf + ARG_MAX);
    
    if (found == false) {
        KernLog("err: command not found: '%.255s' (%ld)\n",
                    shargv[0], strlen(shargv[0]));
    }
}

#define CMDBUFSIZE (BStdOut->lineLen - shpromptlen - 2)

void ShStartShell(void)
{
    uchar ch;
    error_t rc;
    char *ptr; // temp

    // Current line - beginning & current pos
    char *cmdbuf = malloc(CMDBUFSIZE);
    char *bufptr = cmdbuf;
    char *bufend = cmdbuf;

    // History...
    // We use a basic N-entries command history
    #define N 10    // must be >1
    char *history = malloc(CMDBUFSIZE * N);
    int historyIndex = 0;
    int historyScroll = 0;
    
    bool insertMode = 0;
    size_t nLines;

    argvbuf = malloc(ARG_MAX * 2);
    memzero(argvbuf, ARG_MAX * 2);
    shargv = (char **)argvbuf;

    shprompt = malloc(SHPROMPT_MAXLEN);
    strcpy(shprompt, "shell> ");
    shpromptlen = 7;

    KernLog("\n%C%s%C", VGA_COLOR_WHITE, shprompt, shcol);
    BFlushBuf(BStdOut);

    while ((rc = BGetFromBuf(BStdIn, &ch)) == EOK || rc == EENDF) {
        // Reset BStdIn's content
        if (rc == EENDF) {
            if (!(BStdIn->flags & BF_ERR)) {
                *bufptr = 0;
                bufptr = cmdbuf;
                ExecuteCommand(cmdbuf, shcmdtable);

                memzero(cmdbuf, CMDBUFSIZE);
                BFlushBuf(BStdIn);
                KernLog("%C%s%C", VGA_COLOR_WHITE, shprompt, shcol);
                BFlushBuf(BStdOut);
            }
            else break;
        }
    
        switch (ch) {

        // Backspace character
        case K_BACKSPACE:
            if (bufptr == cmdbuf)
                break;

            memmove(bufptr-1, bufptr, bufend-bufptr+1);
            bufptr--;
            bufend--;
            goto print_current_line;

        // DEL character
        case K_DEL:
            if (bufptr == bufend)
                break;

            memmove(bufptr, bufptr+1, bufend-bufptr+1);
            IoSetCursorOffset(IoGetCursorOffset()+1);
            bufend--;
            goto print_current_line;

        case K_BELL:        IoDoBeep();     break;
        case K_ESCAPE:      PoShutdown();   break;
        case K_PAGE_UP:     IoScrollUp();   break;
        case K_PAGE_DOWN:   IoScrollDown(); break;
        
        case K_INSERT:
            insertMode = 1 - insertMode;
            break;
    
        // Move within buffer
        case K_ARRW_LEFT:
            if (!(bufptr > cmdbuf))
                break;

            bufptr--;
            
            IoSetCursorOffset(IoGetCursorOffset()-1);
            BFlushBuf(BStdOut);
            break;
    
        case K_ARRW_RIGHT:
            if (bufptr == bufend)
                break;

            bufptr++;
            IoSetCursorOffset(IoGetCursorOffset()+1);
            BFlushBuf(BStdOut);
            break;
        
        case K_HOME:
            if (bufptr == cmdbuf)
                break;

            IoSetCursorOffset(IoGetCursorOffset()-(int)(bufptr-cmdbuf));
            bufptr = cmdbuf;
            BFlushBuf(BStdOut);
            break;
            
        case K_END:
            if (bufptr == bufend)
                break;

            IoSetCursorOffset(IoGetCursorOffset()+(int)(bufend-bufptr));
            bufptr = bufend;
            BFlushBuf(BStdOut);
            break;

        // Handle history scroll up/down
        case K_ARRW_UP:
        case K_ARRW_DOWN:
            if (historyIndex == 0)
                break;  // No history yet

            if (ch == K_ARRW_UP) {
                memmove(cmdbuf, &history[historyScroll*CMDBUFSIZE], CMDBUFSIZE);
                if (historyScroll > 0)
                    historyScroll--;
            }

            else if (historyScroll < historyIndex-1) {
                historyScroll++;
                memmove(cmdbuf, &history[historyScroll*CMDBUFSIZE], CMDBUFSIZE);
            }

            else
                break;

            for (bufend = cmdbuf; *bufend && bufend < cmdbuf+CMDBUFSIZE; bufend++);
            bufptr = bufend;

            IoSetCursorOffset(0);
            goto print_current_line;

        // Regular character
        default:
            if (bufptr >= bufend) {
                *bufptr++ = (char)ch;

                bufend = bufptr;
                *bufptr = 0;
                
                // Advance cursor
                if (IoGetCursorOffset() < 0)
                    IoSetCursorOffset(IoGetCursorOffset() + 1);
            }

            else {
                if (!insertMode) {
                    *++bufend = 0;
                    for (ptr = bufend-1; ptr != bufptr; ptr--)
                        *ptr = *(ptr - 1);
                }

                else { // insertMode
                    // Advance cursor
                    if (IoGetCursorOffset() < 0)
                        IoSetCursorOffset(IoGetCursorOffset() + 1);
                }

                *bufptr++ = (char)ch;
            }

        print_current_line:

            BLockBuf(BStdOut);

            BStdOut->wp -= BStdOut->lastLF;
            BStdOut->size -= BStdOut->lastLF;
            BStdOut->lastLF = 0;
            bprintf(BStdOut, "%C%s%C%s",
                VGA_COLOR_WHITE, shprompt, shcol, cmdbuf);

            BUnlockBuf(BStdOut);
            
            IoSetScroll(1);
            IoScrollDown();     // This calls the flusher

            // End of buffer?
            if (bufend != cmdbuf+CMDBUFSIZE-1) {
                break; // No
            }

            // Else, *FALLTHROUGH* to case '\n'

       case '\n':
            BPutOnBuf(BStdOut, '\n');

            while (IoGetScroll() > 0) {
                IoScrollDown();
            }

            IoSetCursorOffset(0);

            bufptr = cmdbuf;    // Reset bufptr
            bufend = cmdbuf;

            if (cmdbuf[0] && !isspace(cmdbuf[0])) {
                // Forget old commands
                if (historyIndex >= N) {
                    assert(historyIndex == N);
                    memmove(history, history+CMDBUFSIZE, CMDBUFSIZE * (N-1));
                    historyIndex = historyScroll = N-1;
                    
                }
                // Update history
                memmove(&history[historyIndex*CMDBUFSIZE], cmdbuf, CMDBUFSIZE);
                historyScroll = historyIndex;
                historyIndex++;
                
                // Execute & reset
                ExecuteCommand(cmdbuf, shcmdtable);
                memzero(cmdbuf, CMDBUFSIZE);
            }

            KernLog("%C%s%C", VGA_COLOR_WHITE, shprompt, shcol);
            BFlushBuf(BStdIn);
            BFlushBuf(BStdOut);
            break;
        }

        KePauseCPU();
    }
}