import {
    dateToUint32,
    readFileName,
    writeFileName,
    uint32ToDate,
} from './utils';
import { FileEntry, readEntries, writeEntries } from './file_entry';
import { STORAGE_TYPES, ACCESS_TYPES } from './constants';
import { byte, word } from 'js/types';
import { ProDOSVolume } from '.';

const VDH_BLOCK = 2;
const VDH_OFFSETS = {
    PREV: 0x00,
    NEXT: 0x02,
    STORAGE_TYPE: 0x04,
    NAME_LENGTH: 0x04,
    VOLUME_NAME: 0x05,
    RESERVED_1: 0x14,
    CASE_BITS: 0x1a,
    CREATION: 0x1c,
    VERSION: 0x20,
    MIN_VERSION: 0x21,
    ACCESS: 0x22,
    ENTRY_LENGTH: 0x23,
    ENTRIES_PER_BLOCK: 0x24,
    FILE_COUNT: 0x25,
    BIT_MAP_POINTER: 0x27,
    TOTAL_BLOCKS: 0x29,
} as const;

export class VDH {
    private blocks: Uint8Array[];

    prev: word = 0;
    next: word = 0;
    storageType: byte = STORAGE_TYPES.VDH_HEADER;
    name: string = '';
    creation: Date = new Date();
    access: byte = ACCESS_TYPES.ALL;
    entryLength = 0x27;
    entriesPerBlock = 23;
    fileCount = 0;
    bitMapPointer: word = 0;
    totalBlocks: word = 0;
    entries: FileEntry[] = [];

    constructor(private volume: ProDOSVolume) {
        this.blocks = this.volume.blocks();
    }

    read() {
        const block = new DataView(this.blocks[VDH_BLOCK].buffer);

        this.next = block.getUint16(VDH_OFFSETS.NEXT, true);
        this.storageType = block.getUint8(VDH_OFFSETS.STORAGE_TYPE) >> 4;
        const nameLength = block.getUint8(VDH_OFFSETS.NAME_LENGTH) & 0xf;
        const caseBits = block.getUint8(VDH_OFFSETS.CASE_BITS);
        this.name = readFileName(
            block,
            VDH_OFFSETS.VOLUME_NAME,
            nameLength,
            caseBits
        );
        this.creation = uint32ToDate(
            block.getUint32(VDH_OFFSETS.CREATION, true)
        );
        this.access = block.getUint8(VDH_OFFSETS.ACCESS);
        this.entryLength = block.getUint8(VDH_OFFSETS.ENTRY_LENGTH);
        this.entriesPerBlock = block.getUint8(VDH_OFFSETS.ENTRIES_PER_BLOCK);
        this.fileCount = block.getUint16(VDH_OFFSETS.FILE_COUNT, true);
        this.bitMapPointer = block.getUint16(VDH_OFFSETS.BIT_MAP_POINTER, true);
        this.totalBlocks = block.getUint16(VDH_OFFSETS.TOTAL_BLOCKS, true);

        this.entries = readEntries(this.volume, block, this);
    }

    write() {
        const block = new DataView(this.blocks[VDH_BLOCK].buffer);

        const nameLength = this.name.length & 0x0f;
        block.setUint8(
            VDH_OFFSETS.STORAGE_TYPE,
            (this.storageType << 4) & nameLength
        );
        const caseBits = writeFileName(
            block,
            VDH_OFFSETS.VOLUME_NAME,
            this.name
        );
        block.setUint32(
            VDH_OFFSETS.CREATION,
            dateToUint32(this.creation),
            true
        );
        block.setUint16(VDH_OFFSETS.CASE_BITS, caseBits);
        block.setUint8(VDH_OFFSETS.ACCESS, this.access);
        block.setUint8(VDH_OFFSETS.ENTRY_LENGTH, this.entryLength);
        block.setUint8(VDH_OFFSETS.ENTRIES_PER_BLOCK, this.entriesPerBlock);
        block.setUint16(VDH_OFFSETS.FILE_COUNT, this.fileCount, true);
        block.setUint16(VDH_OFFSETS.BIT_MAP_POINTER, this.bitMapPointer, true);
        block.setUint16(VDH_OFFSETS.TOTAL_BLOCKS, this.totalBlocks, true);

        writeEntries(this.volume, block, this);
    }
}