/**
 * Copyright since 2025 Mifos Initiative
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

import { Component, ElementRef, forwardRef, HostListener, Input, ViewChild } from '@angular/core';
import { CommonModule } from '@angular/common';
import { ControlValueAccessor, FormsModule, NG_VALUE_ACCESSOR } from '@angular/forms';

export interface SearchSelectOption {
  value: string;
  label: string;
  /** What typed text is matched against — defaults to `label` when omitted, but a caller can
   *  pass a richer string (e.g. account no + customer name + branch) so a search hits fields
   *  that aren't all visible in the collapsed label. */
  searchText?: string;
}

/**
 * Drop-in replacement for a plain `<select>` when the option list is long enough that scanning
 * it is impractical (e.g. hundreds of accounts) — a text box that filters the option list as you
 * type, instead of a native dropdown you can only scroll through. Selection only commits on
 * click; typing without picking an option reverts the box to the last committed selection on
 * blur, so the bound ngModel value never drifts from an actual, valid option.
 *
 * Usage: <mifosx-search-select [options]="opts" [(ngModel)]="selectedValue"></mifosx-search-select>
 */
@Component({
  selector: 'mifosx-search-select',
  standalone: true,
  imports: [
    CommonModule,
    FormsModule
  ],
  providers: [
    {
      provide: NG_VALUE_ACCESSOR,
      useExisting: forwardRef(() => SearchSelectComponent),
      multi: true
    }
  ],
  template: `
    <div class="inv-search-select">
      <input
        #inputEl
        type="text"
        class="inv-search-select__input"
        [value]="query"
        [placeholder]="placeholder"
        [disabled]="disabled"
        (input)="onInput($event)"
        (focus)="onFocus()"
        (blur)="onBlur()"
      />
      @if (open) {
        <ul
          class="inv-search-select__list"
          [style.top.px]="listTop"
          [style.left.px]="listLeft"
          [style.width.px]="listWidth"
          (mousedown)="$event.preventDefault()"
        >
          @for (o of filteredOptions; track o.value) {
            <li
              class="inv-search-select__option"
              [class.inv-search-select__option--active]="o.value === value"
              (click)="selectOption(o)"
            >
              {{ o.label }}
            </li>
          } @empty {
            <li class="inv-search-select__empty">No matches</li>
          }
        </ul>
      }
    </div>
  `,
  styles: [
    `
      /* Angular view encapsulation stops the host page's shared styles from reaching inside this
       * component's own template, so its look is re-declared here rather than inherited. */
      :host {
        display: block;
        width: 100%;
      }
      .inv-search-select {
        position: relative;
        width: 100%;
      }
      .inv-search-select__input {
        width: 100%;
        height: 36px;
        padding: 0 10px;
        border: 1px solid #e2e8f0;
        border-radius: 8px;
        font-size: 13px;
        color: #0d1b2a;
        font-family: inherit;
        background: #fff;
        box-sizing: border-box;
      }
      /* position: fixed, anchored via JS to the input's own screen coords (see
       * updateListPosition()) rather than absolute inside this component — most of this app's
       * cards use overflow: hidden for rounded corners, which would otherwise clip a dropdown
       * that extends past the card's edge. */
      .inv-search-select__list {
        position: fixed;
        z-index: 2000;
        max-height: 260px;
        overflow-y: auto;
        margin: 0;
        padding: 4px;
        list-style: none;
        background: #fff;
        border: 1px solid #e2e8f0;
        border-radius: 8px;
        box-shadow: 0 8px 24px rgba(13, 27, 42, 0.18);
      }
      .inv-search-select__option {
        padding: 8px 10px;
        border-radius: 6px;
        font-size: 13px;
        color: #0d1b2a;
        cursor: pointer;
        white-space: nowrap;
        overflow: hidden;
        text-overflow: ellipsis;
      }
      .inv-search-select__option:hover,
      .inv-search-select__option--active {
        background: #eef2ff;
      }
      .inv-search-select__empty {
        padding: 8px 10px;
        font-size: 12px;
        color: #94a3b8;
      }
    `
  ]
})
export class SearchSelectComponent implements ControlValueAccessor {
  @Input() options: SearchSelectOption[] = [];
  @Input() placeholder = 'Search…';

  @ViewChild('inputEl') private inputEl?: ElementRef<HTMLInputElement>;

  value = '';
  query = '';
  open = false;
  disabled = false;

  listTop = 0;
  listLeft = 0;
  listWidth = 0;

  private onChangeFn: (v: string) => void = () => {};
  onTouched: () => void = () => {};

  get filteredOptions(): SearchSelectOption[] {
    const q = this.query.trim().toLowerCase();
    if (!q) {
      return this.options;
    }
    return this.options.filter((o) => (o.searchText || o.label).toLowerCase().includes(q));
  }

  private labelFor(value: string): string {
    return this.options.find((o) => o.value === value)?.label ?? '';
  }

  writeValue(v: string): void {
    this.value = v ?? '';
    this.query = this.labelFor(this.value);
  }

  registerOnChange(fn: (v: string) => void): void {
    this.onChangeFn = fn;
  }

  registerOnTouched(fn: () => void): void {
    this.onTouched = fn;
  }

  setDisabledState(isDisabled: boolean): void {
    this.disabled = isDisabled;
  }

  /** Anchors the fixed-position list to the input's current on-screen box. */
  private updateListPosition(): void {
    const el = this.inputEl?.nativeElement;
    if (!el) {
      return;
    }
    const rect = el.getBoundingClientRect();
    this.listTop = rect.bottom + 4;
    this.listLeft = rect.left;
    this.listWidth = rect.width;
  }

  @HostListener('window:scroll')
  @HostListener('window:resize')
  onWindowChange(): void {
    if (this.open) {
      this.updateListPosition();
    }
  }

  onInput(event: Event): void {
    this.query = (event.target as HTMLInputElement).value;
    this.open = true;
    this.updateListPosition();
  }

  onFocus(): void {
    this.open = true;
    this.updateListPosition();
  }

  onBlur(): void {
    this.open = false;
    this.onTouched();
    // Discard any uncommitted typed text — only a clicked option ever changes `value`.
    this.query = this.labelFor(this.value);
  }

  selectOption(o: SearchSelectOption): void {
    this.value = o.value;
    this.query = o.label;
    this.open = false;
    this.onChangeFn(this.value);
    this.onTouched();
  }
}