import {
  AfterViewChecked,
  Component,
  ElementRef,
  inject,
  OnDestroy,
  OnInit,
  signal,
  ViewChild,
} from '@angular/core';
import { FormControl, ReactiveFormsModule, Validators } from '@angular/forms';
import { Subject, takeUntil } from 'rxjs';
import { MatButtonModule } from '@angular/material/button';
import { MatFormFieldModule } from '@angular/material/form-field';
import { MatIconModule } from '@angular/material/icon';
import { MatInputModule } from '@angular/material/input';
import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
import { MatTooltipModule } from '@angular/material/tooltip';
import { DpService } from 'dp-ui/dp.service';
import { FisAppMessage, MessageHeader, AppMessageType } from 'dp-ui/fisappmessage/apprequestmessagetype';

interface ChatMessage {
  id: string;
  sender: 'user' | 'assistant';
  content: string;
  timestamp: number;
}

function makeWelcome(): ChatMessage {
  return {
    id: 'system-welcome',
    sender: 'assistant',
    content:
      'Welcome to the Industrial Intelligence Portal. Ask me about batch yield summaries, ripeness distributions, ABW trends, or anomaly flags from your production data.',
    timestamp: Date.now(),
  };
}

@Component({
  selector: 'app-chatbot',
  standalone: true,
  imports: [
    ReactiveFormsModule,
    MatButtonModule,
    MatFormFieldModule,
    MatIconModule,
    MatInputModule,
    MatProgressSpinnerModule,
    MatTooltipModule,
  ],
  styleUrl: './chatbot.component.scss',
  template: `
    <div class="chat-shell">

      <!-- Header -->
      <div class="chat-header">
        <mat-icon class="header-icon">psychology</mat-icon>
        <span class="header-title">Intelligence Portal</span>
        <span class="session-tag" [title]="'Session: ' + sessionId()">
          SID·{{ sessionId().slice(-6) }}
        </span>
        <button mat-icon-button
                class="reset-btn"
                type="button"
                (click)="resetSession()"
                matTooltip="Reset session context"
                [disabled]="loading()">
          <mat-icon>refresh</mat-icon>
        </button>
      </div>

      <!-- Message feed -->
      <div class="chat-feed" #messagesEl>
        @for (msg of messages(); track msg.id) {
          <div class="chat-msg" [class.chat-msg--user]="msg.sender === 'user'">
            <span class="chat-msg__label">
              {{ msg.sender === 'user' ? 'You' : 'Intelligence' }}
            </span>
            <div class="chat-msg__bubble">{{ msg.content }}</div>
          </div>
        }
        @if (loading()) {
          <div class="chat-thinking">
            <mat-spinner diameter="14"></mat-spinner>
            <span>Processing…</span>
          </div>
        }
      </div>

      <!-- Composer -->
      <form class="chat-composer" (submit)="send($event)">
        <mat-form-field appearance="outline" subscriptSizing="dynamic" class="chat-input">
          <mat-label>Ask the intelligence layer…</mat-label>
          <input matInput [formControl]="inputControl" autocomplete="off" />
        </mat-form-field>
        <button mat-icon-button
                type="submit"
                class="send-btn"
                [disabled]="loading() || inputControl.invalid">
          <mat-icon>send</mat-icon>
        </button>
      </form>

    </div>
  `,
})
export class ChatbotComponent implements OnInit, AfterViewChecked, OnDestroy {
  private readonly dpService = inject(DpService);

  @ViewChild('messagesEl') messagesEl!: ElementRef<HTMLDivElement>;

  inputControl = new FormControl('', {
    nonNullable: true,
    validators: [Validators.required, Validators.minLength(1)],
  });

  messages = signal<ChatMessage[]>([]);
  loading = signal(false);
  sessionId = signal(crypto.randomUUID());

  private readonly destroy$ = new Subject<void>();
  private pendingScroll = false;

  ngOnInit(): void {
    this.messages.set([makeWelcome()]);
  }

  ngAfterViewChecked(): void {
    if (this.pendingScroll) {
      const el = this.messagesEl?.nativeElement;
      if (el) el.scrollTop = el.scrollHeight;
      this.pendingScroll = false;
    }
  }

  ngOnDestroy(): void {
    this.destroy$.next();
    this.destroy$.complete();
  }

  resetSession(): void {
    this.fisStream('Chat', 'clear', {}).pipe(takeUntil(this.destroy$)).subscribe();
    this.sessionId.set(crypto.randomUUID());
    this.messages.set([makeWelcome()]);
    this.inputControl.reset();
  }

  send(event: Event): void {
    event.preventDefault();
    const text = this.inputControl.value.trim();
    if (!text || this.loading()) return;

    this.inputControl.reset();
    this.messages.update(m => [
      ...m,
      {
        id: crypto.randomUUID(),
        sender: 'user',
        content: text,
        timestamp: Date.now(),
      },
    ]);
    this.loading.set(true);
    this.pendingScroll = true;

    this.fisStream('Chat', 'send', { message: text, sessionId: this.sessionId() })
      .pipe(takeUntil(this.destroy$))
      .subscribe({
        next: (res: any) => {
          const content: string =
            typeof res === 'string'
              ? res
              : Array.isArray(res)
              ? (res[0]?.output ?? res[0]?.text ?? res[0]?.message ?? JSON.stringify(res))
              : (res?.output ?? res?.text ?? res?.message ?? JSON.stringify(res));

          this.messages.update(m => [
            ...m,
            {
              id: crypto.randomUUID(),
              sender: 'assistant',
              content,
              timestamp: Date.now(),
            },
          ]);
          this.loading.set(false);
          this.pendingScroll = true;
        },
        error: () => this.appendError(),
      });
  }

  private fisStream(serviceId: string, operation: string, payload: unknown) {
    const messageID = crypto.randomUUID();
    const message: FisAppMessage = {
      header: {
        messageID,
        serviceId,
        messageName: operation,
        messageType: AppMessageType.Command,
      } as unknown as MessageHeader,
      data: payload,
    };
    return this.dpService.stream(message);
  }

  private appendError(): void {
    this.messages.update(m => [
      ...m,
      {
        id: crypto.randomUUID(),
        sender: 'assistant',
        content:
          'Unable to reach the intelligence layer. Verify the WebSocket connection is active and the backend is running.',
        timestamp: Date.now(),
      },
    ]);
    this.loading.set(false);
    this.pendingScroll = true;
  }
}