import { Component, OnInit, inject, DestroyRef } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormBuilder, FormGroup, Validators, ReactiveFormsModule } from '@angular/forms';
import { Router } from '@angular/router';
import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
import { MatCardModule } from '@angular/material/card';
import { MatButtonModule } from '@angular/material/button';
import { MatIconModule } from '@angular/material/icon';
import { MatInputModule } from '@angular/material/input';
import { MatFormFieldModule } from '@angular/material/form-field';
import { MatSlideToggleModule } from '@angular/material/slide-toggle';
import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
import { MatTooltipModule } from '@angular/material/tooltip';
import { MatDividerModule } from '@angular/material/divider';
import { AdminService } from '../../../core/services/admin.service';
import { GuestSettings } from '../../../core/models/admin.model';

/**
 * GuestSettingsEditComponent
 * 
 * Form component for editing guest access settings.
 * Allows administrators to configure guest user limitations and features.
 * 
 * Features:
 * - Reactive form with validation
 * - Real-time validation errors
 * - Settings preview before save
 * - Form reset functionality
 * - Success/error handling
 * - Navigation back to view mode
 */
@Component({
  selector: 'app-guest-settings-edit',
  standalone: true,
  imports: [
    CommonModule,
    ReactiveFormsModule,
    MatCardModule,
    MatButtonModule,
    MatIconModule,
    MatInputModule,
    MatFormFieldModule,
    MatSlideToggleModule,
    MatProgressSpinnerModule,
    MatTooltipModule,
    MatDividerModule
  ],
  templateUrl: './guest-settings-edit.component.html',
  styleUrl: './guest-settings-edit.component.scss'
})
export class GuestSettingsEditComponent implements OnInit {
  private readonly adminService = inject(AdminService);
  private readonly router = inject(Router);
  private readonly fb = inject(FormBuilder);
  private readonly destroyRef = inject(DestroyRef);

  // Service signals
  readonly settings = this.adminService.guestSettingsState;
  readonly isLoading = this.adminService.isLoadingSettings;
  readonly error = this.adminService.settingsError;

  // Form
  settingsForm!: FormGroup;
  isSubmitting = false;
  originalSettings: GuestSettings | null = null;

  ngOnInit(): void {
    this.initializeForm();
    this.loadSettings();
  }

  /**
   * Initialize the form with validation
   */
  private initializeForm(): void {
    this.settingsForm = this.fb.group({
      guestAccessEnabled: [false],
      maxQuizzesPerDay: [3, [Validators.required, Validators.min(1), Validators.max(100)]],
      maxQuestionsPerQuiz: [10, [Validators.required, Validators.min(1), Validators.max(50)]],
      sessionExpiryHours: [24, [Validators.required, Validators.min(1), Validators.max(168)]],
      upgradePromptMessage: [
        'You\'ve reached your quiz limit. Sign up for unlimited access!',
        [Validators.required, Validators.minLength(10), Validators.maxLength(500)]
      ]
    });
  }

  /**
   * Load existing settings and populate form
   */
  private loadSettings(): void {
    // If settings already loaded, use them
    if (this.settings()) {
      this.populateForm(this.settings()!);
      return;
    }

    // Otherwise fetch settings
    this.adminService.getGuestSettings()
      .pipe(takeUntilDestroyed(this.destroyRef))
      .subscribe(settings => {
        this.populateForm(settings);
      });
  }

  /**
   * Populate form with existing settings
   */
  private populateForm(settings: GuestSettings): void {
    this.originalSettings = settings;
    this.settingsForm.patchValue({
      guestAccessEnabled: settings.guestAccessEnabled,
      maxQuizzesPerDay: settings.maxQuizzesPerDay,
      maxQuestionsPerQuiz: settings.maxQuestionsPerQuiz,
      sessionExpiryHours: settings.sessionExpiryHours,
      upgradePromptMessage: settings.upgradePromptMessage
    });
  }

  /**
   * Submit form and update settings
   */
  onSubmit(): void {
    if (this.settingsForm.invalid || this.isSubmitting) {
      this.settingsForm.markAllAsTouched();
      return;
    }

    this.isSubmitting = true;
    const formData = this.settingsForm.value;

    this.adminService.updateGuestSettings(formData)
      .pipe(takeUntilDestroyed(this.destroyRef))
      .subscribe({
        next: () => {
          this.isSubmitting = false;
          // Navigate back to view page after short delay
          setTimeout(() => {
            this.router.navigate(['/admin/guest-settings']);
          }, 1500);
        },
        error: () => {
          this.isSubmitting = false;
        }
      });
  }

  /**
   * Cancel editing and return to view page
   */
  onCancel(): void {
    if (this.hasUnsavedChanges()) {
      if (confirm('You have unsaved changes. Are you sure you want to cancel?')) {
        this.router.navigate(['/admin/guest-settings']);
      }
    } else {
      this.router.navigate(['/admin/guest-settings']);
    }
  }

  /**
   * Reset form to original values
   */
  onReset(): void {
    if (this.originalSettings) {
      this.populateForm(this.originalSettings);
    }
  }

  /**
   * Check if form has unsaved changes
   */
  hasUnsavedChanges(): boolean {
    if (!this.originalSettings) return false;
    
    const formValue = this.settingsForm.value;
    return (
      formValue.guestAccessEnabled !== this.originalSettings.guestAccessEnabled ||
      formValue.maxQuizzesPerDay !== this.originalSettings.maxQuizzesPerDay ||
      formValue.maxQuestionsPerQuiz !== this.originalSettings.maxQuestionsPerQuiz ||
      formValue.sessionExpiryHours !== this.originalSettings.sessionExpiryHours ||
      formValue.upgradePromptMessage !== this.originalSettings.upgradePromptMessage
    );
  }

  /**
   * Get error message for a form field
   */
  getErrorMessage(fieldName: string): string {
    const field = this.settingsForm.get(fieldName);
    if (!field?.errors || !field.touched) return '';

    if (field.errors['required']) return 'This field is required';
    if (field.errors['min']) return `Minimum value is ${field.errors['min'].min}`;
    if (field.errors['max']) return `Maximum value is ${field.errors['max'].max}`;
    if (field.errors['minlength']) return `Minimum length is ${field.errors['minlength'].requiredLength} characters`;
    if (field.errors['maxlength']) return `Maximum length is ${field.errors['maxlength'].requiredLength} characters`;
    
    return 'Invalid value';
  }

  /**
   * Check if a field has an error
   */
  hasError(fieldName: string): boolean {
    const field = this.settingsForm.get(fieldName);
    return !!(field?.invalid && field?.touched);
  }

  /**
   * Get preview of changes
   */
  getChangesPreview(): Array<{label: string, old: any, new: any}> {
    if (!this.originalSettings || !this.hasUnsavedChanges()) return [];

    const changes: Array<{label: string, old: any, new: any}> = [];
    const formValue = this.settingsForm.value;

    if (formValue.guestAccessEnabled !== this.originalSettings.guestAccessEnabled) {
      changes.push({
        label: 'Guest Access',
        old: this.originalSettings.guestAccessEnabled ? 'Enabled' : 'Disabled',
        new: formValue.guestAccessEnabled ? 'Enabled' : 'Disabled'
      });
    }

    if (formValue.maxQuizzesPerDay !== this.originalSettings.maxQuizzesPerDay) {
      changes.push({
        label: 'Max Quizzes Per Day',
        old: this.originalSettings.maxQuizzesPerDay,
        new: formValue.maxQuizzesPerDay
      });
    }

    if (formValue.maxQuestionsPerQuiz !== this.originalSettings.maxQuestionsPerQuiz) {
      changes.push({
        label: 'Max Questions Per Quiz',
        old: this.originalSettings.maxQuestionsPerQuiz,
        new: formValue.maxQuestionsPerQuiz
      });
    }

    if (formValue.sessionExpiryHours !== this.originalSettings.sessionExpiryHours) {
      changes.push({
        label: 'Session Expiry Hours',
        old: this.originalSettings.sessionExpiryHours,
        new: formValue.sessionExpiryHours
      });
    }

    if (formValue.upgradePromptMessage !== this.originalSettings.upgradePromptMessage) {
      changes.push({
        label: 'Upgrade Prompt Message',
        old: this.originalSettings.upgradePromptMessage,
        new: formValue.upgradePromptMessage
      });
    }

    return changes;
  }

  /**
   * Format expiry time for display
   */
  formatExpiryTime(hours: number): string {
    if (hours < 24) {
      return `${hours} hour${hours !== 1 ? 's' : ''}`;
    }
    const days = Math.floor(hours / 24);
    const remainingHours = hours % 24;
    if (remainingHours === 0) {
      return `${days} day${days !== 1 ? 's' : ''}`;
    }
    return `${days} day${days !== 1 ? 's' : ''} and ${remainingHours} hour${remainingHours !== 1 ? 's' : ''}`;
  }
}