import Foundation

enum RedditThemeStyle {
    static func earlyInjectionScript(isDarkMode: Bool) -> String {
        """
        (function() {
          const wantDark = \(isDarkMode ? "true" : "false");
          window.__reddoraTheme = { wantsDark: wantDark };

          const installMatchMediaOverride = (wantsDark) => {
            if (window.__reddoraTheme.matchMediaInstalled) return;
            const original = window.matchMedia.bind(window);
            window.matchMedia = function(query) {
              const result = original(query);
              if (typeof query === 'string' && query.includes('prefers-color-scheme')) {
                const matches = query.includes('dark') ? wantsDark : !wantsDark;
                return {
                  matches,
                  media: query,
                  onchange: null,
                  addEventListener: (...args) => result.addEventListener(...args),
                  removeEventListener: (...args) => result.removeEventListener(...args),
                  dispatchEvent: (...args) => result.dispatchEvent(...args),
                };
              }
              return result;
            };
            window.__reddoraTheme.matchMediaInstalled = true;
          };

          installMatchMediaOverride(wantDark);
        })();
        """
    }

    static func syncScript(isDarkMode: Bool) -> String {
        """
        (function() {
          const wantDark = \(isDarkMode ? "true" : "false");
          window.__reddoraTheme = window.__reddoraTheme || {};
          window.__reddoraTheme.wantsDark = wantDark;

          const installMatchMediaOverride = (wantsDark) => {
            const original = window.matchMedia.bind(window);
            window.matchMedia = function(query) {
              const result = original(query);
              if (typeof query === 'string' && query.includes('prefers-color-scheme')) {
                const matches = query.includes('dark') ? wantsDark : !wantsDark;
                return {
                  matches,
                  media: query,
                  onchange: null,
                  addEventListener: (...args) => result.addEventListener(...args),
                  removeEventListener: (...args) => result.removeEventListener(...args),
                  dispatchEvent: (...args) => result.dispatchEvent(...args),
                };
              }
              return result;
            };
            window.__reddoraTheme.matchMediaInstalled = true;
          };

          installMatchMediaOverride(wantDark);

          const isDrawerHidden = (element) => !element || (element.offsetWidth === 0 && element.offsetHeight === 0);

          const isRedditDarkModeActive = () => {
            const header = document.querySelector('header');
            const themedNode = header?.firstElementChild;
            if (themedNode) {
              const background = getComputedStyle(themedNode)
                .getPropertyValue('--shreddit-content-background')
                .trim()
                .toLowerCase();
              if (background === '#0e1113' || background === '#1a1a1b') return true;
              if (background === '#ffffff' || background === '#fff') return false;
            }

            const root = document.documentElement;
            if (root.classList.contains('theme-dark')) return true;
            if (root.classList.contains('theme-light')) return false;

            return window.matchMedia('(prefers-color-scheme: dark)').matches;
          };

          const toggleViaDrawer = () => {
            const drawerButton = document.querySelector('#expand-user-drawer-button');
            const drawer = document.querySelector('#user-drawer-content');
            const switchInput = document.querySelector(
              '#darkmode-list-item faceplate-switch-input[name="darkmode-switch-name"]'
            );
            if (!drawerButton || !drawer || !switchInput) return false;

            const drawerWasHidden = isDrawerHidden(drawer);
            if (drawerWasHidden) drawerButton.click();

            const isChecked = switchInput.checked === true
              || switchInput.getAttribute('checked') !== null
              || switchInput.getAttribute('aria-checked') === 'true';
            if (isChecked !== wantDark) {
              switchInput.click();
            }

            if (drawerWasHidden) {
              setTimeout(() => {
                if (!isDrawerHidden(drawer)) drawerButton.click();
              }, 250);
            }

            return true;
          };

          const syncViaAPI = async () => {
            try {
              const response = await fetch('/api/v1/me/prefs', {
                method: 'PATCH',
                headers: { 'Content-Type': 'application/json' },
                credentials: 'same-origin',
                body: JSON.stringify({ nightmode: wantDark }),
              });
              return response.ok;
            } catch {
              return false;
            }
          };

          const run = async () => {
            const current = isRedditDarkModeActive();
            if (current === wantDark) return;

            if (toggleViaDrawer()) return;

            const updated = await syncViaAPI();
            if (updated) {
              window.location.reload();
            }
          };

          if (document.readyState === 'loading') {
            document.addEventListener('DOMContentLoaded', () => run(), { once: true });
          } else {
            run();
          }
        })();
        """
    }
}