#include "progs.h"

#define BLOCKSIZE 0x10000 // 64K
#define BLOCKMASK ~0xffff // block = (offset & blockMask)
#define BLOCKSHIFT 16 // blockSize = 1 << blockShift
#define MAXFILESIZE 0x80000000 // 2GB
#define TOTALBLOCKS (MAXFILESIZE/BLOCKSIZE)
uint16_t writtenMap[TOTALBLOCKS];
uint32_t blockLenMap[TOTALBLOCKS];
// NOTE This is linked at the end of program BSS section,
// so that it can be expanded without telling C how much
// it actually needs
uint8_t writeStoreBase[BLOCKSIZE] __attribute__((section(".bss.end")));
void HexEditor(uint8_t *path, VOLINFO *vi) {
    uint32_t err;
    uint16_t *vga_text = (uint16_t *)0xb8000;
    uint32_t screenSize = 80*25;
    uint8_t *scratch = (uint8_t *)0x20000;
    uint8_t (*writeStore)[BLOCKSIZE] = &writeStoreBase;
    for (int i = 0; i < TOTALBLOCKS; i++)
        writtenMap[i] = 0;
    uint8_t *screenBuff = *writeStore;
    // First two blocks are screen buffer
    uint32_t nextFreeBlock = 2;

    FILEINFO fi;
    vga_text = (uint16_t *)0xb8000;
    for (int i = 0; i < 80*50; i++)
        vga_text[i] = 0x0f00;
    err = DFS_OpenFile(vi, path, DFS_READ | DFS_WRITE, scratch, &fi);
    if (err) {
        vga_text += printStr("Open Error: ", vga_text);
        printDword(err, vga_text);
        kbd_wait();
        return;
    }
    if (fi.filelen == 0) {
        vga_text += printStr("File ", vga_text);
        vga_text += printStr((char*)path, vga_text);
        vga_text += printStr(" has no data.", vga_text);
        kbd_wait();
        return;
    }
    if (fi.filelen > MAXFILESIZE) {
        vga_text += printStr("File ", vga_text);
        vga_text += printStr((char*)path, vga_text);
        vga_text += printStr(" is too large (> 2GB).", vga_text);
        kbd_wait();
        return;
    }
    uint32_t drawOffset = 0, lastDrawOffset = -1;
    char cont = 1;
    uint32_t byteCount = 16*24, lastByteCount = 0;
    // Cursor offset from *drawOff*
    int32_t cursorScreenOff = 0, lastCursorScreenOff = -1;
    // Pointer to last cursor in *VGA mem*
    uint8_t *lastCursorScreenPtr = (uint8_t*)0xb8000;
    char cursorNibble = 1, lastCursorNibble = 0;
    char cursorRedraw = 1;
    char reread = 1, redraw = 1;
    uint8_t *currBuff = 0, *nextBuff = 0;
    uint32_t currBuffLength, nextBuffLength, totalBuffLength;
    uint16_t currLoadedBlock = -1, nextLoadedBlock = -1;
    char currInMap = 0, nextInMap = 0;
    uint32_t changeOffset = -1, lastChangeOffset = -1;
    char fileChanged = 0;
    for (;cont;) {
        // Check if we need to scroll screen for cursor
        // Should never be more than 16 away, if it is,
        // things will be caught by sanity checks.
        // Scroll Back
        if (cursorScreenOff < 0) {
            if (drawOffset - 16 < fi.filelen)
                drawOffset -= 16;
            cursorScreenOff += 16;
        }
        // Scroll Forward
        if (cursorScreenOff >= byteCount) {
            if (drawOffset + 16 < fi.filelen)
                drawOffset += 16;
            cursorScreenOff -= 16;
        }

        // Sanity checks
        if (cursorScreenOff >= byteCount)
            cursorScreenOff = byteCount - 1;
        if (cursorScreenOff + drawOffset >= fi.filelen)
            cursorScreenOff = fi.filelen - drawOffset - 1;
        if (cursorScreenOff < 0) cursorScreenOff = 0;

        if (cursorNibble != lastCursorNibble)
            cursorRedraw = 1;
        if (cursorScreenOff != lastCursorScreenOff)
            cursorRedraw = 1;
        if (cursorRedraw) {
            const uint32_t hexViewScreenOff = 10 * 2;
            const uint32_t asciiViewScreenOff = 61 * 2;
            uint16_t *screen = (uint16_t*)0xb8000;
            // Byte draw starts on first line
            uint16_t *line = &screen[80 * (1 + (cursorScreenOff >> 4))];
            uint8_t *cursorPtr = (uint8_t*)line;
            if (cursorNibble == 0) {
                // Each byte takes 3 chars on screen
                cursorPtr += hexViewScreenOff + (cursorScreenOff & 0xF) * 3 * 2;
                if ((cursorScreenOff & 0xF) > 7)
                    cursorPtr += 2;
                // Low nibble
                cursorPtr += 2;
            } else if (cursorNibble == 1) {
                // Each byte takes 3 chars on screen
                cursorPtr += hexViewScreenOff + (cursorScreenOff & 0xF) * 3 * 2;
                if ((cursorScreenOff & 0xF) > 7)
                    cursorPtr += 2;
            // ASCII area
            } else {
                // Each byte takes 1 char on screen
                cursorPtr += asciiViewScreenOff + (cursorScreenOff & 0xF) * 2;
            }
            // We want the color byte, not char
            cursorPtr++;
            if (cursorPtr != lastCursorScreenPtr) {
                *lastCursorScreenPtr = 0x0f;
                *cursorPtr = 0xf0;
                lastCursorScreenPtr = cursorPtr;
            }
            lastCursorScreenOff = cursorScreenOff;
            lastCursorNibble = cursorNibble;
            cursorRedraw = 0;
        }

        if ((drawOffset & BLOCKMASK) != (lastDrawOffset & BLOCKMASK)) {
            lastDrawOffset = (drawOffset & BLOCKMASK);
            reread = 1;
            redraw = 1;
        }
        if (drawOffset != lastDrawOffset) {
            lastDrawOffset = drawOffset;
            redraw = 1;
        }
        if (byteCount != lastByteCount) {
            lastByteCount = byteCount;
            redraw = 1;
        }
        if (changeOffset != lastChangeOffset) {
            redraw = 1;
            lastChangeOffset = changeOffset;
        }
        // Check for changes to block
        if (changeOffset != -1) {
            char isCurr = changeOffset < BLOCKSIZE;
            char changeInMap = isCurr ? currInMap : nextInMap;
            uint8_t *changedBlock = isCurr ? currBuff : nextBuff;
            // If changes are in map we don't need to do anything
            if (!changeInMap) {
                uint16_t loadedBlock = isCurr ? currLoadedBlock : nextLoadedBlock;
                uint16_t storeBlockIdx = writtenMap[loadedBlock];
                // Add a new map entry
                if (!storeBlockIdx) {
                    writtenMap[loadedBlock] = storeBlockIdx = nextFreeBlock++;
                    blockLenMap[loadedBlock] = isCurr ? currBuffLength : nextBuffLength;
                }
                uint8_t *storeBlock = writeStore[storeBlockIdx];
                for (int i = 0; i < BLOCKSIZE; i++)
                    storeBlock[i] = changedBlock[i];
                // Move the current buffer to map
                if (isCurr) { currBuff = storeBlock; currInMap = 1; }
                else { nextBuff = storeBlock; nextInMap = 1; }
            }
            changeOffset = -1;
            fileChanged = 1;
            redraw = 1;
        }

        if (reread) {
            // TODO We should probably check if we already have
            // the block to read in nextBuff from previous stuff
            // We are in a modified block
            uint16_t newBlock = drawOffset >> BLOCKSHIFT;
            if (writtenMap[newBlock]) {
                currBuff = writeStore[writtenMap[newBlock]];
                currBuffLength = blockLenMap[newBlock];
                totalBuffLength = currBuffLength;
                currInMap = 1;
            // We are in an unmodified block
            } else {
                uint32_t blockOffset = drawOffset & BLOCKMASK;
                vga_text = &((uint16_t*)0xb8000)[80];
                DFS_Seek(&fi, blockOffset, scratch);
                if (fi.pointer != blockOffset) {
                    vga_text += printStr("Seek Error", vga_text);
                    kbd_wait();
                    return;
                }
                err = DFS_ReadFile(&fi, scratch, screenBuff, &currBuffLength, BLOCKSIZE);
                if (err && err != DFS_EOF) {
                    vga_text += printStr("Read Error: ", vga_text);
                    printDword(err, vga_text);
                    kbd_wait();
                    return;
                }
                currBuff = screenBuff;
                totalBuffLength = currBuffLength;
                currInMap = 0;
            }
            currLoadedBlock = newBlock;
            reread = 0;
            nextInMap = 0;
        }
        // We will be drawing stuff in the next block
        // TODO This would be better served with nice functions!
        if (currBuffLength == BLOCKSIZE && (drawOffset & ~BLOCKMASK) > (BLOCKSIZE - byteCount)) {
            // TODO We should probably check if we already have
            // the next block in currBuff from previous stuff
            // Next is a modified block
            uint16_t newBlock = (drawOffset >> BLOCKSHIFT) + 1;
            if (nextLoadedBlock != newBlock) {
                if (writtenMap[newBlock]) {
                    nextBuffLength = blockLenMap[newBlock];
                    nextBuff = writeStore[writtenMap[newBlock]];
                    nextInMap = 1;
                // Next is an unmodified block
                } else {
                    uint32_t blockOffset = (drawOffset & BLOCKMASK) + BLOCKSIZE;
                    vga_text = &((uint16_t*)0xb8000)[80];
                    DFS_Seek(&fi, blockOffset, scratch);
                    if (fi.pointer != blockOffset) {
                        vga_text += printStr("Seek Error", vga_text);
                        kbd_wait();
                        return;
                    }
                    err = DFS_ReadFile(&fi, scratch, &screenBuff[BLOCKSIZE], &nextBuffLength, BLOCKSIZE);
                    if (err && err != DFS_EOF) {
                        vga_text += printStr("Read Error: ", vga_text);
                        printDword(err, vga_text);
                        kbd_wait();
                        return;
                    }
                    nextBuff = &screenBuff[BLOCKSIZE];
                    nextInMap = 0;
                }
                nextLoadedBlock = newBlock;
            }
            totalBuffLength = currBuffLength + nextBuffLength;
        }
        if (redraw) {
            vga_text = (uint16_t *)0xb8000;
            vga_text += printStr((char*)path, vga_text);
            vga_text += printChar(fileChanged ? '*' : ' ', vga_text);
            {
                const char prnt[] = "Scroll: Up/Down PgUp/PgDown Home/End             Exit: F1";
                vga_text = &((uint16_t*)0xb8000)[80-sizeof(prnt)];
                vga_text += printStr((char*)prnt, vga_text);
            }
            vga_text = &((uint16_t*)0xb8000)[80];
            uint32_t offsetInBuff = drawOffset & ~BLOCKMASK;
            uint8_t *drawFromBuff = &currBuff[offsetInBuff];
            uint32_t maxDrawLen = totalBuffLength - (drawOffset & ~BLOCKMASK);
            for (int i = 0; i < maxDrawLen && i < byteCount; i += 16) {
                // Blocks are BLOCKSIZE aligned, so 16-byte alignment should work
                if (i + offsetInBuff >= BLOCKSIZE) {
                    drawFromBuff = &nextBuff[-i];
                    offsetInBuff = 0;
                }
                vga_text += printDword(i + drawOffset, vga_text);
                vga_text += printChar(' ', vga_text);
                vga_text += printChar(' ', vga_text);
                for (uint32_t j = 0; j < 16; j++) {
                    if (i + j < maxDrawLen)
                        vga_text += printByte(drawFromBuff[i + j], vga_text);
                    else {
                        vga_text += printChar(' ', vga_text);
                       vga_text += printChar(' ', vga_text);
                    }
                    vga_text += printChar(' ', vga_text);
                    if (j == 7)
                        vga_text += printChar(' ', vga_text);
                }
                vga_text += printChar(' ', vga_text);
                vga_text += printChar('|', vga_text);
                for (uint32_t j = 0; j < 16; j++) {
                    if (i + j < maxDrawLen)
                        vga_text += printChar(drawFromBuff[i + j], vga_text);
                    else vga_text += printChar(' ', vga_text);
                }
                vga_text += printChar('|', vga_text);
                vga_text = nextLine(vga_text,(uint16_t*)0xb8000);
            }
            // Clear remainder of screen
            for (;vga_text < &((uint16_t*)0xb8000)[screenSize]; vga_text++)
                *vga_text = 0x0f00;
            redraw = 0;
        }
        uint16_t key = get_scancode();
        union V86Regs_t regs;
        FARPTR v86_entry;
        char try_edit = 0;
        switch (key & 0xff) {
            case KEY_DOWN:
                // Stay in file
                if ((cursorScreenOff + 16 + drawOffset) < fi.filelen)
                    cursorScreenOff += 16;
                break;
            case KEY_UP:
                // Stay in file
                if ((uint32_t)(cursorScreenOff - 16 + drawOffset) < fi.filelen)
                    cursorScreenOff -= 16;
                break;
            case KEY_LEFT:
                if (cursorNibble == 0) { cursorNibble = 1; break; }
                // Exiting text area
                else if (cursorNibble == 2 && (cursorScreenOff & 0xF) == 0) {
                    cursorNibble = 0;
                    cursorScreenOff |= 0xF;
                // Stay in file
                } else if ((cursorScreenOff - 1 + drawOffset) < fi.filelen) {
                    cursorScreenOff--;
                    if (cursorNibble == 1) cursorNibble = 0;
                }
                break;
            case KEY_RIGHT:
                if (cursorNibble == 1) { cursorNibble = 0; break; }
                // Entering text area
                else if (cursorNibble == 0 && (cursorScreenOff & 0xF) == 0xF) {
                    cursorNibble = 2;
                    cursorScreenOff &= ~0xF;
                // Stay in file
                } else if ((cursorScreenOff + 1 + drawOffset) < fi.filelen) {
                    cursorScreenOff++;
                    if (cursorNibble == 0) cursorNibble = 1;
                }
                break;
            case KEY_PGDOWN:
                if (drawOffset + byteCount < fi.filelen)
                    drawOffset += byteCount;
                else if ((fi.filelen / byteCount) * byteCount > drawOffset)
                    drawOffset = (fi.filelen / byteCount) * byteCount;
                break;
            case KEY_PGUP:
                if (drawOffset - byteCount < fi.filelen)
                    drawOffset -= byteCount;
                else drawOffset = 0;
                break;
            case KEY_HOME:
                cursorScreenOff &= ~0xF;
                if (cursorNibble == 0) cursorNibble = 1;
                break;
            case KEY_END:
                cursorScreenOff |= 0xF;
                if (cursorNibble == 1) cursorNibble = 0;
                break;
            case KEY_F1:
                cont = 0;
                break;
            case KEY_F3: // start of file
                drawOffset = 0;
                break;
            case KEY_F4: // end of file
                if ((fi.filelen / byteCount) * byteCount > drawOffset)
                    drawOffset = (fi.filelen / byteCount) * byteCount;
                break;
            case KEY_F6: // TODO write file
                break;
            case KEY_F2:
                if (byteCount != 16*24) {
                    SetVideo25Lines();
                    SetCursorDisabled();
                    screenSize = 80*25;
                    byteCount = 16*24;
                }
                break;
            case KEY_F5:
                if (byteCount != 16*49) {
                    SetVideo50Lines();
                    SetCursorDisabled();
                    screenSize = 80*50;
                    byteCount = 16*49;
                }
                break;
            default:
                try_edit = 1;
                break;
        }
        if (!try_edit) continue;
        // Check if in range
        char k = key >> 8; // ASCII portion
        char v;
        if (cursorNibble == 2 && k >= 0x20 && k <= 0x7E) v = k;
        else if (k >= '0' && k <= '9')
            v = k - '0';
        else if (k >= 'a' && k <= 'f')
            v = k - 'a' + 0xA;
        else if (k >= 'A' && k <= 'F')
            v = k - 'A' + 0xA;
        else continue;
        // Change buffer at cursor
        uint32_t screenOffsetInBuff = drawOffset & ~BLOCKMASK;
        changeOffset = screenOffsetInBuff + cursorScreenOff;
        char isCurr = changeOffset < BLOCKSIZE;
        uint8_t *changeBuff = isCurr ? currBuff : nextBuff;
        uint32_t changeOffsetInBuff = isCurr ? changeOffset : changeOffset - BLOCKSIZE;
        if (cursorNibble == 0)
            changeBuff[changeOffsetInBuff] = (changeBuff[changeOffsetInBuff] & 0xF0) | v;
        else if (cursorNibble == 1)
            changeBuff[changeOffsetInBuff] = (changeBuff[changeOffsetInBuff] & 0x0F) | (v << 4);
        else changeBuff[changeOffsetInBuff] = v;
        redraw = 1;
    }
    if (!fileChanged) return;
    vga_text = (uint16_t*)0xb8000;
    vga_text += printStr((char*)path, vga_text);
    vga_text += printChar(fileChanged ? '*' : ' ', vga_text);
    vga_text += printChar(' ', vga_text);
    vga_text += printStr("Save changes to file? (Y/N)", vga_text);
    for (;vga_text < &((uint16_t*)0xb8000)[80];vga_text++)
        *vga_text = 0x0f00;
    uint16_t key=0;
    for(;(key & 0xff) != KEY_N && (key & 0xff) != KEY_Y;key = get_scancode());
    if ((key & 0xff) != KEY_Y) return;
    // Write changes
    for (int i = 0; i < TOTALBLOCKS && (i << BLOCKSHIFT) < fi.filelen; i++) {
        // No change in current block
        uint16_t blockIdx = writtenMap[i];
        uint32_t blockLen = blockLenMap[i];
        if (!blockIdx) continue;
        // Write block to file
        uint32_t successcount;
        uint32_t blockOff = i << BLOCKSHIFT;
        DFS_Seek(&fi, blockOff, scratch);
        if (fi.pointer != blockOff) {
            vga_text = (uint16_t*)0xb8000;
            vga_text += printStr("Seek Error ", vga_text);
            kbd_wait();
            return;
        }
        uint32_t err = DFS_WriteFile(&fi, scratch, writeStore[blockIdx], &successcount, blockLen);
        if (successcount < blockLen || err) {
            vga_text = (uint16_t*)0xb8000;
            vga_text += printStr("Write Error ", vga_text);
            kbd_wait();
            return;
        }
    }
}