import localforage from 'localforage';
import type { CustomTheme, LoadedCustomTheme } from '@/types/CustomThemes';
import { settingsState } from '@/seqta/utils/listeners/SettingsState';
import debounce from '@/seqta/utils/debounce';

type ThemeContent = {
  id: string;
  name: string;
  coverImage?: string; // base64, optional
  description: string;
  defaultColour?: string;
  CanChangeColour?: boolean;
  CustomCSS?: string;
  hideThemeName?: boolean;
  forceDark?: boolean;
  images: { id: string, variableName: string, data: string }[]; // data: base64
};

export class ThemeManager {
  private static instance: ThemeManager;
  private currentTheme: CustomTheme | null = null;
  private styleElement: HTMLStyleElement | null = null;
  private previewStyleElement: HTMLStyleElement | null = null;
  private previousImageVariableNames: string[] = [];
  private originalPreviewColor: string | null = null;
  private originalPreviewTheme: boolean | null = null;
  private imageUrlCache: Map<string, string> = new Map();

  private constructor() {
    console.debug('[ThemeManager] Initializing...');
  }

  public static getInstance(): ThemeManager {
    if (!ThemeManager.instance) {
      ThemeManager.instance = new ThemeManager();
    }
    return ThemeManager.instance;
  }

  /**
   * Get the currently active theme
   */
  public getCurrentTheme(): CustomTheme | null {
    return this.currentTheme;
  }

  /**
   * Get a theme by ID from storage
   */
  public async getTheme(themeId: string): Promise<CustomTheme | null> {
    console.debug('[ThemeManager] Getting theme:', themeId);
    try {
      const theme = await localforage.getItem(themeId) as CustomTheme;
      return theme;
    } catch (error) {
      console.error('[ThemeManager] Error getting theme:', error);
      return null;
    }
  }

  /**
   * Get the ID of the currently selected theme
   */
  public getSelectedThemeId(): string {
    return settingsState.selectedTheme;
  }

  /**
   * Disable the current theme without deleting it
   */
  public async disableTheme(): Promise<void> {
    console.debug('[ThemeManager] Disabling current theme');
    try {
      if (!this.currentTheme) {
        console.debug('[ThemeManager] No theme to disable');
        return;
      }

      await this.removeTheme(this.currentTheme);
      this.currentTheme = null;
      settingsState.selectedTheme = '';
      console.debug('[ThemeManager] Theme disabled successfully');
    } catch (error) {
      console.error('[ThemeManager] Error disabling theme:', error);
    }
  }

  /**
   * Initialize the theme system and restore previous state
   */
  public async initialize(): Promise<void> {
    console.debug('[ThemeManager] Starting initialization');
    try {
      // Check if theme creator was open during reload
      const themeCreatorOpen = localStorage.getItem('themeCreatorOpen');
      if (themeCreatorOpen === 'true') {
        console.debug('[ThemeManager] Theme creator was open, clearing preview state');
        this.clearPreview();
        // Clean up the flag
        localStorage.removeItem('themeCreatorOpen');
      }
      
      if (settingsState.selectedTheme) {
        console.debug('[ThemeManager] Found selected theme, restoring:', settingsState.selectedTheme);
        await this.setTheme(settingsState.selectedTheme);
      }
    } catch (error) {
      console.error('[ThemeManager] Error during initialization:', error);
    }
  }

  /**
   * Clean up theme system resources
   */
  public async cleanup(): Promise<void> {
    console.debug('[ThemeManager] Cleaning up resources');
    try {
      if (this.currentTheme) {
        await this.removeTheme(this.currentTheme);
      }
    } catch (error) {
      console.error('[ThemeManager] Error during cleanup:', error);
    }
  }

  /**
   * Set and apply a theme by ID
   */
  public async setTheme(themeId: string): Promise<void> {
    console.debug('[ThemeManager] Setting theme:', themeId);
    try {
      const theme = await localforage.getItem(themeId) as CustomTheme;
      if (!theme) {
        console.error('[ThemeManager] Theme not found:', themeId);
        return;
      }

      // Store original settings before applying new theme
      if (!settingsState.selectedTheme) {
        console.debug('[ThemeManager] Storing original settings');
        settingsState.originalSelectedColor = settingsState.selectedColor;
        settingsState.originalDarkMode = settingsState.DarkMode;
      }

      // Remove current theme if exists
      if (this.currentTheme) {
        console.debug('[ThemeManager] Removing current theme');
        await this.removeTheme(this.currentTheme);
      }

      // Apply new theme
      await this.applyTheme(theme);
      this.currentTheme = theme;
      settingsState.selectedTheme = themeId;

    } catch (error) {
      console.error('[ThemeManager] Error setting theme:', error);
    }
  }

  /**
   * Apply theme components (CSS, images, settings)
   */
  private async applyTheme(theme: CustomTheme): Promise<void> {
    console.debug('[ThemeManager] Applying theme:', theme.name);
    try {
      // Apply custom CSS
      if (theme.CustomCSS) {
        console.debug('[ThemeManager] Applying custom CSS');
        this.applyCustomCSS(theme.CustomCSS);
      }

      // Apply custom images
      if (theme.CustomImages) {
        console.debug('[ThemeManager] Applying custom images');
        theme.CustomImages.forEach((image) => {
          const imageUrl = URL.createObjectURL(image.blob);
          document.documentElement.style.setProperty('--' + image.variableName, `url(${imageUrl})`);
        });
      }

      // Apply theme settings
      if (theme.forceDark !== undefined) {
        console.debug('[ThemeManager] Setting dark mode:', theme.forceDark);
        settingsState.DarkMode = theme.forceDark;
      }

      if (theme.defaultColour) {
        console.debug('[ThemeManager] Setting color:', theme.defaultColour);
        settingsState.selectedColor = theme.defaultColour;
      }

    } catch (error) {
      console.error('[ThemeManager] Error applying theme:', error);
    }
  }

  /**
   * Remove theme and restore original settings
   */
  private async removeTheme(theme: CustomTheme): Promise<void> {
    console.debug('[ThemeManager] Removing theme:', theme.name);
    try {
      // Remove custom CSS
      if (this.styleElement) {
        console.debug('[ThemeManager] Removing custom CSS');
        this.styleElement.remove();
        this.styleElement = null;
      }

      // Remove custom images
      if (theme.CustomImages) {
        console.debug('[ThemeManager] Removing custom images');
        theme.CustomImages.forEach((image) => {
          const value = document.documentElement.style.getPropertyValue('--' + image.variableName);
          if (value) {
            URL.revokeObjectURL(value.slice(4, -1)); // Remove url() wrapper
          }
          document.documentElement.style.removeProperty('--' + image.variableName);
        });
      }

      // Restore original settings
      if (settingsState.originalSelectedColor) {
        console.debug('[ThemeManager] Restoring original color:', settingsState.originalSelectedColor);
        settingsState.selectedColor = settingsState.originalSelectedColor;
      }

      if (settingsState.originalDarkMode !== undefined) {
        console.debug('[ThemeManager] Restoring original dark mode:', settingsState.originalDarkMode);
        settingsState.DarkMode = settingsState.originalDarkMode;
        settingsState.originalDarkMode = undefined;
      }

      this.currentTheme = null;
      settingsState.selectedTheme = '';

    } catch (error) {
      console.error('[ThemeManager] Error removing theme:', error);
    }
  }

  /**
   * Apply custom CSS to the document
   */
  private applyCustomCSS(css: string): void {
    console.debug('[ThemeManager] Applying custom CSS');
    try {
      if (!this.styleElement) {
        this.styleElement = document.createElement('style');
        this.styleElement.id = 'custom-theme';
        document.head.appendChild(this.styleElement);
      }
      this.styleElement.textContent = css;
    } catch (error) {
      console.error('[ThemeManager] Error applying custom CSS:', error);
    }
  }

  /**
   * Get list of available themes
   */
  public async getAvailableThemes(): Promise<CustomTheme[]> {
    console.debug('[ThemeManager] Getting available themes');
    try {
      const themeIds = await localforage.getItem('customThemes') as string[] | null;
      if (!themeIds) {
        return [];
      }

      const themes = await Promise.all(
        themeIds.map(async (id) => {
          return await localforage.getItem(id) as CustomTheme;
        })
      );

      return themes.filter(theme => theme !== null);
    } catch (error) {
      console.error('[ThemeManager] Error getting available themes:', error);
      return [];
    }
  }

  /**
   * Save or update a theme
   */
  public async saveTheme(theme: LoadedCustomTheme): Promise<void> {
    console.debug('[ThemeManager] Saving theme:', theme.name);
    try {
      await localforage.setItem(theme.id, theme);
      const themeIds = await localforage.getItem('customThemes') as string[] | null;
      
      if (themeIds) {
        if (!themeIds.includes(theme.id)) {
          themeIds.push(theme.id);
          await localforage.setItem('customThemes', themeIds);
        }
      } else {
        await localforage.setItem('customThemes', [theme.id]);
      }
    } catch (error) {
      console.error('[ThemeManager] Error saving theme:', error);
    }
  }

  /**
   * Delete a theme
   */
  public async deleteTheme(themeId: string): Promise<void> {
    console.debug('[ThemeManager] Deleting theme:', themeId);
    try {
      const theme = await localforage.getItem(themeId) as CustomTheme;
      if (theme) {
        if (this.currentTheme?.id === themeId) {
          await this.removeTheme(theme);
        }
        await localforage.removeItem(themeId);
        
        const themeIds = await localforage.getItem('customThemes') as string[] | null;
        if (themeIds) {
          const updatedThemeIds = themeIds.filter(id => id !== themeId);
          await localforage.setItem('customThemes', updatedThemeIds);
        }
      }
    } catch (error) {
      console.error('[ThemeManager] Error deleting theme:', error);
    }
  }

  /**
   * Download and install a theme from the store
   */
  public async downloadTheme(themeContent: { id: string; name: string; description: string; coverImage: string; }): Promise<void> {
    console.debug('[ThemeManager] Downloading theme:', themeContent.name);
    try {
      if (!themeContent.id) return;

      const response = await fetch(`https://raw.githubusercontent.com/BetterSEQTA/BetterSEQTA-Themes/main/store/themes/${themeContent.id}/theme.json`);
      const themeData = await response.json() as ThemeContent;
      
      await this.installTheme(themeData);
    } catch (error) {
      console.error('[ThemeManager] Error downloading theme:', error);
    }
  }

  /**
   * Install a theme from theme data
   */
  public async installTheme(themeData: ThemeContent): Promise<void> {
    console.debug('[ThemeManager] Installing theme:', themeData.name);
    try {
      // Validate required fields
      if (!themeData.id || !themeData.name) {
        throw new Error('Theme is missing required fields (id or name)');
      }

      // Handle cover image (optional)
      let coverImageBlob = null;
      if (themeData.coverImage) {
        try {
          const strippedCoverImage = this.stripBase64Prefix(themeData.coverImage);
          coverImageBlob = this.base64ToBlob(strippedCoverImage);
        } catch (e) {
          console.warn('[ThemeManager] Failed to process cover image:', e);
          // Continue without cover image
        }
      }

      // Handle images (optional)
      const images = themeData.images?.map((image) => {
        try {
          if (!image.id || !image.variableName || !image.data) {
            console.warn('[ThemeManager] Skipping invalid image:', image);
            return null;
          }
          return {
            ...image,
            blob: this.base64ToBlob(this.stripBase64Prefix(image.data))
          };
        } catch (e) {
          console.warn('[ThemeManager] Failed to process image:', e);
          return null;
        }
      }).filter(img => img !== null) ?? [];

      // Create theme with defaults for optional fields
      const theme: LoadedCustomTheme = {
        id: themeData.id,
        name: themeData.name,
        description: themeData.description || '',
        webURL: themeData.id,
        coverImage: coverImageBlob,
        CustomImages: images,
        CustomCSS: themeData.CustomCSS || '',
        defaultColour: themeData.defaultColour || 'rgba(0, 123, 255, 1)',
        CanChangeColour: themeData.CanChangeColour ?? true,
        allowBackgrounds: true,
        isEditable: false,
        hideThemeName: themeData.hideThemeName ?? false,
        forceDark: themeData.forceDark
      };

      await this.saveTheme(theme);
    } catch (error) {
      console.error('[ThemeManager] Error installing theme:', error);
      throw error; // Re-throw to handle in UI
    }
  }

  /**
   * Share a theme by exporting it
   */
  public async shareTheme(themeId: string): Promise<void> {
    console.debug('[ThemeManager] Sharing theme:', themeId);
    try {
      const theme = await localforage.getItem(themeId) as LoadedCustomTheme;
      if (!theme) {
        console.error('[ThemeManager] Theme not found');
        return;
      }

      const { CustomImages = [], coverImage, ...themeWithoutImages } = theme;

      // Convert images to base64
      const finalImages = await Promise.all(CustomImages.map(async (image) => ({
        id: image.id,
        variableName: image.variableName,
        data: await this.blobToBase64(image.blob)
      })));

      // Convert cover image to base64
      const coverImageBase64 = coverImage ? await this.blobToBase64(coverImage) : null;

      // Create shareable theme data
      const shareableTheme = {
        ...themeWithoutImages,
        images: finalImages,
        coverImage: coverImageBase64
      };

      // Save theme file
      this.saveThemeFile(shareableTheme, theme.name || 'Unnamed_Theme');
    } catch (error) {
      console.error('[ThemeManager] Error sharing theme:', error);
    }
  }

  /**
   * Preview a theme without applying it
   */
  public async previewTheme(theme: LoadedCustomTheme): Promise<void> {
    console.debug('[ThemeManager] Previewing theme:', theme.name);
    try {
      const { CustomCSS, CustomImages, defaultColour, forceDark } = theme;

      // Store original settings only if this is a new theme
      if (!theme.webURL) {
        if (this.originalPreviewColor === null) {
          this.originalPreviewColor = settingsState.selectedColor;
          localStorage.setItem('originalPreviewColor', settingsState.selectedColor);
        }
        if (this.originalPreviewTheme === null) {
          this.originalPreviewTheme = settingsState.DarkMode;
        }
      }

      // Apply custom CSS
      if (CustomCSS) {
        this.applyPreviewCSS(CustomCSS);
      }

      // Apply custom images
      const newImageVariableNames = CustomImages.map(image => image.variableName);

      // Remove old preview images
      this.previousImageVariableNames.forEach(variableName => {
        if (!newImageVariableNames.includes(variableName)) {
          this.removeImageFromDocument(variableName);
        }
      });

      // Apply new images
      CustomImages.forEach((image) => {
        const imageUrl = URL.createObjectURL(image.blob);
        document.documentElement.style.setProperty(`--${image.variableName}`, `url(${imageUrl})`);
      });

      // Update previousImageVariableNames
      this.previousImageVariableNames = newImageVariableNames;

      // Apply theme settings only if this is a new theme
      if (!theme.webURL) {
        if (forceDark !== undefined) {
          settingsState.DarkMode = forceDark;
        }
        if (defaultColour) {
          settingsState.selectedColor = defaultColour;
        }
      }
    } catch (error) {
      console.error('[ThemeManager] Error previewing theme:', error);
    }
  }

  /**
   * Update the preview of a theme in real-time (for theme creator)
   */
  public async updatePreview(theme: Partial<LoadedCustomTheme>): Promise<void> {
    console.debug('[ThemeManager] Updating theme preview');
    try {
      // Only store original settings if this is a new theme (not editing)
      // We can tell it's a new theme if it has no webURL (which is set when a theme is saved/loaded)
      if (!theme.webURL) {
        if (this.originalPreviewColor === null) {
          this.originalPreviewColor = settingsState.selectedColor;
        }
        if (this.originalPreviewTheme === null) {
          this.originalPreviewTheme = settingsState.DarkMode;
        }
      }

      // Apply CSS if changed
      if (theme.CustomCSS !== undefined) {
        this.applyPreviewCSS(theme.CustomCSS);
      }

      // Handle images if present
      if (theme.CustomImages) {
        const newImageVariableNames = theme.CustomImages.map(image => image.variableName);

        // Remove old preview images that are no longer present
        this.previousImageVariableNames.forEach(variableName => {
          if (!newImageVariableNames.includes(variableName)) {
            this.removeImageFromDocument(variableName);
            // Clean up cached URL
            this.imageUrlCache.delete(variableName);
          }
        });

        // Apply or update images
        theme.CustomImages.forEach((image) => {
          const existingUrl = this.imageUrlCache.get(image.variableName);
          if (!existingUrl) {
            // Only create new URL if one doesn't exist
            const imageUrl = URL.createObjectURL(image.blob);
            this.imageUrlCache.set(image.variableName, imageUrl);
            document.documentElement.style.setProperty(`--${image.variableName}`, `url(${imageUrl})`);
          } else {
            // Reuse existing URL
            document.documentElement.style.setProperty(`--${image.variableName}`, `url(${existingUrl})`);
          }
        });

        this.previousImageVariableNames = newImageVariableNames;
      }

      // Update theme settings only if this is a new theme
      if (!theme.webURL) {
        if (theme.forceDark !== undefined) {
          settingsState.DarkMode = theme.forceDark;
        }
        if (theme.defaultColour) {
          settingsState.selectedColor = theme.defaultColour;
        }
      }
    } catch (error) {
      console.error('[ThemeManager] Error updating theme preview:', error);
    }
  }

  /**
   * Update the preview of a theme (debounced)
   * @param theme - The theme to update the preview of
   */
  public updatePreviewDebounced = debounce((theme: Partial<LoadedCustomTheme>): void => {
    this.updatePreview(theme);
  }, 2);

  /**
   * Clear theme preview
   */
  public clearPreview(): void {
    console.debug('[ThemeManager] Clearing theme preview');
    try {
      // Remove preview images and revoke URLs
      this.previousImageVariableNames.forEach(variableName => {
        this.removeImageFromDocument(variableName);
      });
      // Clear all cached URLs
      this.imageUrlCache.forEach(url => URL.revokeObjectURL(url));
      this.imageUrlCache.clear();
      this.previousImageVariableNames = [];

      // Remove preview CSS
      if (this.previewStyleElement) {
        this.previewStyleElement.remove();
        this.previewStyleElement = null;
      }

      // Restore original settings
      const storedColor = localStorage.getItem('originalPreviewColor');
      
      if (storedColor) {
        settingsState.selectedColor = storedColor;
        localStorage.removeItem('originalPreviewColor');
      } else if (this.originalPreviewColor !== null) {
        console.debug('[ThemeManager] Restoring color from memory:', this.originalPreviewColor);
        settingsState.selectedColor = this.originalPreviewColor;
        console.debug('[ThemeManager] Color after restore:', settingsState.selectedColor);
      } else {
        console.debug('[ThemeManager] No color to restore found');
      }
      this.originalPreviewColor = null;

      if (this.originalPreviewTheme !== null) {
        console.debug('[ThemeManager] Restoring dark mode:', this.originalPreviewTheme);
        settingsState.DarkMode = this.originalPreviewTheme;
        this.originalPreviewTheme = null;
      }
    } catch (error) {
      console.error('[ThemeManager] Error clearing preview:', error);
    }
  }

  // Utility methods
  private stripBase64Prefix(base64String: string): string {
    if (!base64String) return '';
    
    const prefixRegex = /^data:[^;]+;base64,/;
    try {
      return prefixRegex.test(base64String) ? base64String.replace(prefixRegex, '') : base64String;
    } catch(err) {
      console.error('[ThemeManager] Error stripping base64 prefix:', err);
      return '';
    }
  }

  private base64ToBlob(base64: string): Blob {
    try {
      const byteString = atob(base64);
      const ab = new ArrayBuffer(byteString.length);
      const ia = new Uint8Array(ab);
      
      for (let i = 0; i < byteString.length; i++) {
        ia[i] = byteString.charCodeAt(i);
      }
      
      return new Blob([ab], { type: 'image/png' });
    } catch(err) {
      console.error('[ThemeManager] Error converting base64 to blob:', err);
      return new Blob();
    }
  }

  private async blobToBase64(blob: Blob): Promise<string> {
    return new Promise((resolve, reject) => {
      const reader = new FileReader();
      reader.onloadend = () => {
        const base64String = reader.result as string;
        const base64Data = base64String.split(',')[1];
        resolve(base64Data);
      };
      reader.onerror = reject;
      reader.readAsDataURL(blob);
    });
  }

  private saveThemeFile(data: object, fileName: string): void {
    try {
      const fileData = JSON.stringify(data, null, 2);
      const blob = new Blob([fileData], { type: 'application/json' });
      const url = URL.createObjectURL(blob);
      const a = document.createElement('a');
      a.href = url;
      a.download = `${fileName}.theme.json`;
      document.body.appendChild(a);
      a.click();
      document.body.removeChild(a);
      URL.revokeObjectURL(url);
    } catch(err) {
      console.error('[ThemeManager] Error saving theme file:', err);
    }
  }

  private removeImageFromDocument(variableName: string): void {
    try {
      const value = document.documentElement.style.getPropertyValue('--' + variableName);
      if (value) {
        const url = this.imageUrlCache.get(variableName);
        if (url) {
          URL.revokeObjectURL(url);
          this.imageUrlCache.delete(variableName);
        }
      }
      document.documentElement.style.removeProperty('--' + variableName);
    } catch(err) {
      console.error('[ThemeManager] Error removing image from document:', err);
    }
  }

  private applyPreviewCSS(css: string): void {
    console.debug('[ThemeManager] Applying preview CSS');
    try {
      if (!this.previewStyleElement) {
        this.previewStyleElement = document.createElement('style');
        this.previewStyleElement.id = 'custom-theme-preview';
        document.head.appendChild(this.previewStyleElement);
      }
      this.previewStyleElement.textContent = css;
    } catch (error) {
      console.error('[ThemeManager] Error applying preview CSS:', error);
    }
  }
}