type outputMapItem = {
    size: number,
    byte: number,
    offset: number,
    name: string,
    value: any
}

class OutputMap {
    mapping: outputMapItem[];
    /**
     * Helper to encode input buffer from process value  
     */
    constructor() {
        this.mapping = [];
    }

    /**
     * Add a bit value to encode
     * 
     * @param byte - Which byte to start at
     * @param offset - Number of bits to offset
     * @param name - Unique name to reference value
     * @param value - Initial value
     */
    addBit(byte: number, offset: number, name: string, value: boolean = false): void {
        this.mapping.push({
            size: 1,
            byte: byte,
            offset: offset,
            name: name,
            value: value
        });

    }

    /**
     * Add a 16 bit integer value to encode
     * 
     * @param byte - Number off bytes to offset
     * @param name - Unique name to reference value
     * @param value - Initial value
     */
    addInt(byte: number, name: string, value: number = 0): void {
        this.mapping.push({
            size: 16,
            byte: byte,
            offset: null,
            name: name,
            value: value
        });

    }

    /**
     * Reads encodes each map process value and writes to buffer
     * 
     * @param data - Device output buffer 
     * @returns Device output buffer encoded with values
     */
    _writeMap(data: Buffer): Buffer {
        this.mapping.forEach(map => {
            switch (map.size) {
            case 1:
                (map.value) ? data[map.byte] |= (1 << map.offset) : data[map.byte] &= ~(1 << map.offset);
                break;
            case 16:
                data.writeUInt16LE(map.value, map.byte);
                break;
            }
        });

        return data;
    }

    /**
     * Set a process value for a output buffer
     * 
     * @param name - Name of map item
     * @param data - Device input buffer
     * @param value - New value to send to device
     * @returns Output buffer to send to device
     */
    setValue(name: string, value: any, data: Buffer): Buffer {
        this.mapping[this.mapping.findIndex(map => map.name === name)].value = value;
        return this._writeMap(data);
    }

    /**
     * Get array of names assigned to mappings
     * 
     * @returns Array of names
     */
    getNames(): string[] {
        return this.mapping.map(item => item.name);
    }

}

export default OutputMap;