class BaseParser {
    constructor(body, curByte = 0, curIndex = 1) {
        // 读取到当前字节数
        this.curByte = curByte;
        // 读取字节的位置
        this.curIndex = curIndex;
        // uint8array => h264 unit info
        this.body = body;
    }
    /**
     * leadingzerobits：1前面的0个数
     * read_bits：读取1后面leadingzerobits位
     * codeNum = 2^leadingzerobits − 1 + read_bits( leadingZeroBits )
     * @returns code_num
     */
    readUV() {
        let leadingzerobits = 0,
            biteVal = 0;
        while (!biteVal) {
            biteVal = readBit(this.body[this.curByte], this.curIndex);
            if (biteVal === 0) {
                leadingzerobits++;
            }
            if (this.curIndex === 8) {
                this.curIndex = 1;
                this.curByte++;
            } else {
                this.curIndex++;
            }
        }
        let code_num = "";
        for (let index = 0; index < leadingzerobits; index++) {
            code_num += readBit(this.body[this.curByte], this.curIndex);
            if (this.curIndex === 8) {
                this.curIndex = 1;
                this.curByte++;
            } else {
                this.curIndex++;
            }
        }
        return 2 ** leadingzerobits - 1 + parseInt(code_num, 2);
    }
    /**
     * 第一步，通过bs_read_ue()，获取codeNum的值。
     * 第二步：根据codeNum的奇偶性，计算出se(v)编码前的值
     *        codeNum & 0x01: 如果为奇数，codeNum = (codeNum + 1)/2
     *                      : 如果为偶数，codeNum = -(codeNum/2)
     * @returns code_num
     */
    readSE() {
        const code_num = this.readUV(this.body);
        const isOdd = code_num % 2 === 1;
        return isOdd ? (code_num + 1) / 2 : -(code_num / 2);
    }
    /**
     * 读取指定位数的数据
     * @param {number} len
     */
    readBits(len) {
        const code_num = "";
        for (let index = 0; index < len; index++) {
            code_num += readBit(this.body[this.curByte], this.curIndex);
            if (this.curIndex === 8) {
                this.curIndex = 1;
                this.curByte++;
            } else {
                this.curIndex++;
            }
        }
        return parseInt(code_num, 2);
    }
}
class Sps extends BaseParser {
    constructor(body) {
        super(body);

        this.profile_idc = this.readBits(8);

        for (let index = 0; index < 6; index++) {
            this[`constraint_set${index}_flag`] = this.readBits(1);
        }
        this.reserved_zero_2bits = this.readBits(2);

        this.level_idc = this.readBits(8);

        this.seq_parameter_set_id = this.readUV();

        this.log2_max_frame_num_minus4 = this.readUV();

        this.pic_order_cnt_type = this.readUV();

        if (this.pic_order_cnt_type === 0) {
            this.log2_max_pic_order_cnt_lsb_minus4 = readUV();
        } else if (this.pic_order_cnt_type === 1) {
            this.delta_pic_order_always_zero_flag = this.readBits(1);
            this.offset_for_non_ref_pic = this.readSE();
            this.offset_for_top_to_bottom_field = this.readSE();
            this.num_ref_frames_in_pic_order_cnt_cycle = this.readUV();
            this.offset_for_ref_frame = [];
            for (let index = 0; index < this.num_ref_frames_in_pic_order_cnt_cycle; index++) {
                this.offset_for_ref_frame.push(this.readSE());
            }
            this.max_num_ref_frames = this.readUV();
            this.gaps_in_frame_num_value_allowed_flag = this.readBits(1);
            this.pic_width_in_mbs_minus1 = this.readUV();
            this.pic_height_in_map_units_minus1 = this.readUV();
            this.frame_mbs_only_flag = this.readBits(1);

            if (!this.frame_mbs_only_flag) {
                this.mb_adaptive_frame_field_flag = this.readBits(1);
            }
            this.direct_8x8_inference_flag = this.readBits(1);
            this.frame_cropping_flag = this.readBits(1);
            if (this.frame_cropping_flag) {
                this.frame_crop_left_offset = this.readUV();
                this.frame_crop_right_offset = this.readUV();
                this.frame_crop_top_offset = this.readUV();
                this.frame_crop_bottom_offset = this.readUV();
            }
            this.vui_parameters_present_flag = this.readBits(1);
        }
    }
}

class Pps extends BaseParser {
    constructor(body) {
        super(body);

        this.pic_parameter_set_id = this.readUV();
        this.seq_parameter_set_id = this.readUV();
        this.entropy_coding_mode_flag = this.readBits(1);
        this.num_slice_groups_minus1 = this.readUV();
        if (this.num_slice_groups_minus1 > 0) {
            this.slice_group_map_type = this.readUV();
            if (this.slice_group_map_type == 0) {
                this.run_length_minus1 = [];
                for (let index = 0; index < this.num_slice_groups_minus1; index++) {
                    this.run_length_minus1.push(this.readUV());
                }
            } else if (this.slice_group_map_type == 2) {
                this.top_left = [];
                this.bottom_right = [];
                for (let index = 0; index < this.num_slice_groups_minus1; index++) {
                    this.top_left.push(this.readUV());
                    this.bottom_right.push(this.readUV());
                }
            } else if (this.slice_group_map_type === 3 || this.slice_group_map_type === 4 || this.slice_group_map_type === 5) {
                this.slice_group_change_direction_flag = this.readBits(1);
                this.slice_group_change_rate_minus1 = this.readUV();
            } else if (this.slice_group_map_type == 6) {
                this.pic_size_in_map_units_minus1 = this.readUV();
                this.slice_group_id = [];
                for (let index = 0; index < this.pic_size_in_map_units_minus1; index++) {
                    this.slice_group_id.push(this.readUV());
                }
            }
        }

        this.num_ref_idx_10_default_active_minus1 = this.readUV();
        this.num_ref_idx_11_default_active_minus1 = this.readUV();
        this.weighted_pred_flag = this.readBits(1);
        this.weighted_bipred_idc = this.readBits(2);
        this.pic_init_qp_minus26 = this.readSE();
        this.pic_init_qs_minus26 = this.readSE();
        this.chroma_qp_index_offset = this.readSE();
        this.deblocking_filter_control_present_flag = this.readBits(1);
        this.constrained_intra_pred_flag = this.readBits(1);
        this.redundant_pic_present_flag = this.readBits(1);

        // if (more_rbsp_data())
    }
}

/**
 * 读取指定位置的值
 * @param {*} val
 * @param {*} index
 * @param {*} direction
 * @returns
 */
function readBit(val, index, direction = "ltr") {
    if (direction === "rtl") {
        return (val >> (index - 1)) & 0x01;
    } else if (direction === "ltr") {
        return (val >> (8 - index)) & 0x01;
    }
}

export function SpsParser(body) {
    return new Sps(body);
}

export function PpsParser(body) {
    return new Pps(body);
}