import { Directive, ElementRef, Input } from '@angular/core';
import { HostListener } from '@angular/core';

@Directive({
    // tslint:disable-next-line: directive-selector
    selector: '[number-only]'
})
export class NumberOnlyDirective {

    @Input() precision: number;

    constructor(private element: ElementRef) {}

    @HostListener('keydown', ['$event'])
    onKeyDown(e: KeyboardEvent) {
        const val = (e.target as any).value;
        const key = e.key;
        const checkKeys = ['.', '-', '%'];
        const selectionVal = this.getSelectionValue(e.target);
        if (val && checkKeys.indexOf(key) > -1 && val.indexOf(key) > -1  && !(selectionVal && selectionVal.indexOf(key) > -1) ) {
            e.preventDefault();
        }

        if (
            [46, 8, 9, 27, 13, 110, 190, 173].indexOf(e.keyCode) !== -1 ||
            // 允许全选: Ctrl+A
            (e.keyCode === 65 && (e.ctrlKey || e.metaKey)) ||
            // 允许复制: Ctrl+C
            (e.keyCode === 67 && (e.ctrlKey || e.metaKey)) ||
            // 允许粘贴: Ctrl+V
            (e.keyCode === 86 && (e.ctrlKey || e.metaKey)) ||
            // 允许剪切: Ctrl+X
            (e.keyCode === 88 && (e.ctrlKey || e.metaKey)) ||
            // 允许: home（头）, end（尾）, left（左移）, right（右移）
            (e.keyCode >= 35 && e.keyCode <= 39) ||
            e.keyCode === 189
        ) {
            // let it happen, don't do anything
            return;
        }
        // 确保数字以外的案件被拒绝执行默认动作
        if ((e.shiftKey || (e.keyCode < 48 || e.keyCode > 57)) && (e.keyCode < 96 || e.keyCode > 105)) {
            e.preventDefault();
        }

        // 判断当前小数精度
        if (val.indexOf('.') > -1 && this.precision) {
            const curPos = (e.target as any).selectionStart;
            const selectionEnd = (e.target as any).selectionEnd;
            const _precision = val.split('.')[1].length;

            const dotPos = val.indexOf('.');
            if (curPos > dotPos) {
                const selectionText = val.substring(curPos, selectionEnd);
                if (_precision - selectionText.length >= Number(this.precision)) {
                    e.preventDefault();
                    return false;
                }
            }
        }
    }


    private getSelectionValue(target) {
        const start = (target as any).selectionStart;
        const end = (target as any).selectionEnd;
        return target.value.substring(start, end);
    }

    // @HostListener('compositionstart', ['$event']) onCompositionstart(e: KeyboardEvent) {
    //     e.preventDefault();
    //     console.log('compositionstart');
    //     console.log(e);
    //     e.returnValue = false;
    // }
}