import React, { useState, useRef, useEffect } from 'react';
import styled from '@emotion/styled';
import { useTranslation } from 'react-i18next';
import { useTheme } from '../../contexts/ThemeContext';
import { spacing, borderRadius, animation, sizing } from '../../theme';

// SVG Icons (inline for no external dependencies)
const SunIcon: React.FC<{ size?: number }> = ({ size = 20 }) => (
  <svg
    width={size}
    height={size}
    viewBox="0 0 24 24"
    fill="none"
    stroke="currentColor"
    strokeWidth="2"
    strokeLinecap="round"
    strokeLinejoin="round"
  >
    <circle cx="12" cy="12" r="5" />
    <line x1="12" y1="1" x2="12" y2="3" />
    <line x1="12" y1="21" x2="12" y2="23" />
    <line x1="4.22" y1="4.22" x2="5.64" y2="5.64" />
    <line x1="18.36" y1="18.36" x2="19.78" y2="19.78" />
    <line x1="1" y1="12" x2="3" y2="12" />
    <line x1="21" y1="12" x2="23" y2="12" />
    <line x1="4.22" y1="19.78" x2="5.64" y2="18.36" />
    <line x1="18.36" y1="5.64" x2="19.78" y2="4.22" />
  </svg>
);

const MoonIcon: React.FC<{ size?: number }> = ({ size = 20 }) => (
  <svg
    width={size}
    height={size}
    viewBox="0 0 24 24"
    fill="none"
    stroke="currentColor"
    strokeWidth="2"
    strokeLinecap="round"
    strokeLinejoin="round"
  >
    <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z" />
  </svg>
);

const SystemIcon: React.FC<{ size?: number }> = ({ size = 20 }) => (
  <svg
    width={size}
    height={size}
    viewBox="0 0 24 24"
    fill="none"
    stroke="currentColor"
    strokeWidth="2"
    strokeLinecap="round"
    strokeLinejoin="round"
  >
    <rect x="2" y="3" width="20" height="14" rx="2" ry="2" />
    <line x1="8" y1="21" x2="16" y2="21" />
    <line x1="12" y1="17" x2="12" y2="21" />
  </svg>
);

type ThemeMode = 'dark' | 'light' | 'system';

const themeOptionDefs: { value: ThemeMode; labelKey: string; icon: React.ReactNode }[] = [
  { value: 'dark', labelKey: 'theme.dark', icon: <MoonIcon size={16} /> },
  { value: 'light', labelKey: 'theme.light', icon: <SunIcon size={16} /> },
  { value: 'system', labelKey: 'theme.system', icon: <SystemIcon size={16} /> },
];

export const ThemeToggle: React.FC = () => {
  const { t } = useTranslation();
  const { theme, setTheme, resolvedTheme } = useTheme();
  const [isOpen, setIsOpen] = useState(false);
  const containerRef = useRef<HTMLDivElement>(null);

  // Close dropdown when clicking outside
  useEffect(() => {
    const handleClickOutside = (event: MouseEvent) => {
      if (containerRef.current && !containerRef.current.contains(event.target as Node)) {
        setIsOpen(false);
      }
    };

    if (isOpen) {
      document.addEventListener('mousedown', handleClickOutside);
    }

    return () => {
      document.removeEventListener('mousedown', handleClickOutside);
    };
  }, [isOpen]);

  // Close on escape key
  useEffect(() => {
    const handleEscape = (event: KeyboardEvent) => {
      if (event.key === 'Escape') {
        setIsOpen(false);
      }
    };

    if (isOpen) {
      document.addEventListener('keydown', handleEscape);
    }

    return () => {
      document.removeEventListener('keydown', handleEscape);
    };
  }, [isOpen]);

  // Determine which icon to show based on theme state
  const getCurrentIcon = () => {
    if (theme === 'system') {
      return <SystemIcon />;
    }
    return resolvedTheme === 'dark' ? <MoonIcon /> : <SunIcon />;
  };

  const handleSelect = (value: ThemeMode) => {
    setTheme(value);
    setIsOpen(false);
  };

  return (
    <ToggleContainer ref={containerRef}>
      <ToggleButton
        onClick={() => setIsOpen(!isOpen)}
        aria-label={t('theme.toggleMenu')}
        aria-expanded={isOpen}
        aria-haspopup="listbox"
        title={t('theme.currentTheme', { theme: theme === 'system' ? t('theme.system') : resolvedTheme })}
      >
        {getCurrentIcon()}
      </ToggleButton>

      {isOpen && (
        <Dropdown role="listbox" aria-label={t('theme.selectTheme')}>
          {themeOptionDefs.map((option) => (
            <DropdownItem
              key={option.value}
              onClick={() => handleSelect(option.value)}
              role="option"
              aria-selected={theme === option.value}
              isActive={theme === option.value}
            >
              <IconWrapper>{option.icon}</IconWrapper>
              <span>{t(option.labelKey)}</span>
            </DropdownItem>
          ))}
        </Dropdown>
      )}
    </ToggleContainer>
  );
};

const ToggleContainer = styled.div`
  position: relative;
  display: inline-block;
`;

const ToggleButton = styled.button`
  display: flex;
  align-items: center;
  justify-content: center;
  width: ${sizing.button.lg}px;
  height: ${sizing.button.lg}px;
  background: var(--bg-surface);
  border: 1px solid var(--border-default);
  border-radius: ${borderRadius.md}px;
  cursor: pointer;
  color: var(--fg-primary);
  transition: all ${animation.duration.normal} ${animation.easing.default};

  &:hover {
    background: var(--accent-subtle);
    border-color: var(--accent-border);
    transform: translateY(-2px);
  }

  &:focus {
    outline: none;
    box-shadow: 0 0 0 2px rgba(0, 145, 152, 0.3);
  }

  &:active {
    transform: translateY(0);
  }

  svg {
    flex-shrink: 0;
  }
`;

const Dropdown = styled.div`
  position: absolute;
  top: calc(100% + ${spacing.sm}px);
  right: 0;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: ${borderRadius.sm}px;
  padding: ${spacing.xs}px;
  min-width: 140px;
  z-index: 1000;
  box-shadow: var(--shadow-lg);
`;

const DropdownItem = styled.button<{ isActive: boolean }>`
  display: flex;
  align-items: center;
  gap: ${spacing.sm}px;
  width: 100%;
  padding: ${spacing.sm}px ${spacing.md}px;
  background: ${props => props.isActive ? 'var(--accent-subtle)' : 'transparent'};
  border: none;
  border-radius: ${borderRadius.sm}px;
  cursor: pointer;
  color: ${props => props.isActive ? 'var(--accent-text)' : 'var(--fg-primary)'};
  font-size: 14px;
  text-align: left;
  transition: background ${animation.duration.fast} ${animation.easing.default};

  &:hover {
    background: ${props => props.isActive ? 'var(--accent-subtle)' : 'var(--bg-hover)'};
  }

  &:focus {
    outline: none;
    background: var(--accent-subtle);
  }
`;

const IconWrapper = styled.span`
  display: flex;
  align-items: center;
  justify-content: center;
  width: ${sizing.icon.sm}px;
  height: ${sizing.icon.sm}px;
`;