export type CategoryGroup = 'development' | 'testing' | 'implementation' | 'other';

export const DEFAULT_TEST_CATEGORY_ID = 'cat-test-functional';

export interface TaskCategory {
  id: string;
  code: string;
  name: string;
  group: CategoryGroup;
  color?: string;
  sortOrder: number;
  isSystem: boolean;
}

export const CATEGORY_GROUP_LABEL: Record<CategoryGroup, string> = {
  development: '开发',
  testing: '测试',
  implementation: '实施',
  other: '其他',
};

export const PRESET_CATEGORIES: TaskCategory[] = [
  { id: 'cat-1', code: 'frontend_development', name: '前端开发', group: 'development', color: '#3b82f6', sortOrder: 1, isSystem: true },
  { id: 'cat-frontend-interaction', code: 'frontend_interaction', name: '前端交互', group: 'development', color: '#0ea5e9', sortOrder: 2, isSystem: true },
  { id: 'cat-2', code: 'backend_development', name: '后端开发', group: 'development', color: '#6366f1', sortOrder: 3, isSystem: true },
  { id: 'cat-backend-api', code: 'backend_api', name: '后端接口', group: 'development', color: '#2563eb', sortOrder: 4, isSystem: true },
  { id: 'cat-3', code: 'database_schema', name: '数据库设计', group: 'development', color: '#8b5cf6', sortOrder: 5, isSystem: true },
  { id: 'cat-4', code: 'api_integration', name: '接口联调', group: 'development', color: '#06b6d4', sortOrder: 6, isSystem: true },
  { id: DEFAULT_TEST_CATEGORY_ID, code: 'test_functional', name: '功能测试', group: 'testing', color: '#22c55e', sortOrder: 20, isSystem: true },
  { id: 'cat-test-ui-interaction', code: 'test_ui_interaction', name: 'UI交互测试', group: 'testing', color: '#06b6d4', sortOrder: 21, isSystem: true },
  { id: 'cat-test-form-validation', code: 'test_form_validation', name: '表单校验测试', group: 'testing', color: '#84cc16', sortOrder: 22, isSystem: true },
  { id: 'cat-test-api', code: 'test_api', name: '接口测试', group: 'testing', color: '#14b8a6', sortOrder: 23, isSystem: true },
  { id: 'cat-test-data-consistency', code: 'test_data_consistency', name: '数据一致性测试', group: 'testing', color: '#10b981', sortOrder: 24, isSystem: true },
  { id: 'cat-test-permission', code: 'test_permission', name: '权限测试', group: 'testing', color: '#8b5cf6', sortOrder: 25, isSystem: true },
  { id: 'cat-test-exception', code: 'test_exception', name: '异常场景测试', group: 'testing', color: '#f97316', sortOrder: 26, isSystem: true },
  { id: 'cat-test-boundary', code: 'test_boundary', name: '边界值测试', group: 'testing', color: '#f59e0b', sortOrder: 27, isSystem: true },
  { id: 'cat-test-state-flow', code: 'test_state_flow', name: '状态流转测试', group: 'testing', color: '#6366f1', sortOrder: 28, isSystem: true },
  { id: 'cat-test-compatibility', code: 'test_compatibility', name: '兼容性测试', group: 'testing', color: '#a855f7', sortOrder: 29, isSystem: true },
  { id: 'cat-test-regression', code: 'test_regression', name: '回归测试', group: 'testing', color: '#64748b', sortOrder: 30, isSystem: true },
  { id: 'cat-5', code: 'data_processing', name: '数据处理', group: 'implementation', color: '#f59e0b', sortOrder: 40, isSystem: true },
  { id: 'cat-6', code: 'implementation_support', name: '实施支持', group: 'implementation', color: '#10b981', sortOrder: 41, isSystem: true },
  { id: 'cat-other-doc', code: 'documentation', name: '文档', group: 'other', color: '#64748b', sortOrder: 60, isSystem: true },
];

const LEGACY_CODE_BY_ID: Record<string, string> = {
  'cat-1': 'frontend_development',
  'cat-2': 'backend_development',
  'cat-3': 'database_schema',
  'cat-4': 'api_integration',
  'cat-5': 'data_processing',
  'cat-6': 'implementation_support',
};

function slugifyCategoryName(name: string, index: number): string {
  return (
    name
      .trim()
      .toLowerCase()
      .replace(/[^a-z0-9\u4e00-\u9fa5]+/g, '_')
      .replace(/^_+|_+$/g, '') || `category_${index + 1}`
  );
}

function normalizeCategoryNameForMatch(name: string): string {
  return name.trim().toLowerCase().replace(/\s+/g, '');
}

function hashCategoryName(name: string): string {
  let hash = 0;
  for (let i = 0; i < name.length; i++) {
    hash = (hash * 31 + name.charCodeAt(i)) | 0;
  }
  return Math.abs(hash).toString(36);
}

function uniqueCategoryCode(base: string, categories: TaskCategory[]): string {
  if (!categories.some((category) => category.code === base)) return base;
  let suffix = 2;
  while (categories.some((category) => category.code === `${base}_${suffix}`)) suffix++;
  return `${base}_${suffix}`;
}

function uniqueAiCategoryId(name: string, categories: TaskCategory[]): string {
  const base = `cat-ai-${hashCategoryName(name)}-${categories.length + 1}`;
  if (!categories.some((category) => category.id === base)) return base;
  let suffix = 2;
  while (categories.some((category) => category.id === `${base}-${suffix}`)) suffix++;
  return `${base}-${suffix}`;
}

export function normalizeTaskCategory(category: Partial<TaskCategory> | undefined, index = 0): TaskCategory {
  const preset = PRESET_CATEGORIES.find((c) => c.id === category?.id);
  const name = category?.name || preset?.name || `分类 ${index + 1}`;
  return {
    id: category?.id || preset?.id || `cat-${index + 1}`,
    code: category?.code || LEGACY_CODE_BY_ID[category?.id ?? ''] || preset?.code || slugifyCategoryName(name, index),
    name,
    group: category?.group || preset?.group || 'other',
    color: category?.color ?? preset?.color,
    sortOrder: typeof category?.sortOrder === 'number' ? category.sortOrder : preset?.sortOrder ?? index + 1,
    isSystem: typeof category?.isSystem === 'boolean' ? category.isSystem : Boolean(preset?.isSystem),
  };
}

export function normalizeTaskCategories(categories: Partial<TaskCategory>[] = []): TaskCategory[] {
  const merged: Partial<TaskCategory>[] = Array.isArray(categories) ? [...categories] : [];
  for (const preset of PRESET_CATEGORIES) {
    if (!merged.some((c) => c.id === preset.id)) merged.push(preset);
  }
  return merged.map((category, index) => normalizeTaskCategory(category, index));
}

export function getCategoryById(categories: TaskCategory[], id: string): TaskCategory | undefined {
  return categories.find((c) => c.id === id);
}

export function getCategoriesByGroup(categories: TaskCategory[], group: CategoryGroup): TaskCategory[] {
  return categories.filter((c) => c.group === group).sort((a, b) => a.sortOrder - b.sortOrder);
}

export function findCategoryByCode(categories: TaskCategory[], code?: string): TaskCategory | undefined {
  if (!code) return undefined;
  return categories.find((c) => c.code === code);
}

export function getDefaultCategoryByGroup(categories: TaskCategory[], group: CategoryGroup): TaskCategory {
  return getCategoriesByGroup(categories, group)[0] ?? categories[0] ?? PRESET_CATEGORIES[0];
}

export function resolveCategoryIdFromCode(categories: TaskCategory[], code: string | undefined, fallbackGroup: CategoryGroup): string {
  return findCategoryByCode(categories, code)?.id ?? getDefaultCategoryByGroup(categories, fallbackGroup).id;
}

export function ensureTaskCategoryByName(
  categories: TaskCategory[],
  name: string | undefined,
  group: CategoryGroup,
): { categories: TaskCategory[]; category: TaskCategory; created: boolean } {
  const normalizedCategories = normalizeTaskCategories(categories);
  const trimmedName = name?.trim() ?? '';
  if (!trimmedName) {
    return {
      categories: normalizedCategories,
      category: getDefaultCategoryByGroup(normalizedCategories, group),
      created: false,
    };
  }

  const targetKey = normalizeCategoryNameForMatch(trimmedName);
  const existing = normalizedCategories.find(
    (category) => category.group === group && normalizeCategoryNameForMatch(category.name) === targetKey,
  );
  if (existing) {
    return { categories: normalizedCategories, category: existing, created: false };
  }

  const codeBase = slugifyCategoryName(trimmedName, normalizedCategories.length);
  const category: TaskCategory = {
    id: uniqueAiCategoryId(trimmedName, normalizedCategories),
    code: uniqueCategoryCode(codeBase, normalizedCategories),
    name: trimmedName,
    group,
    sortOrder: Math.max(0, ...normalizedCategories.map((item) => item.sortOrder)) + 1,
    isSystem: false,
  };

  return {
    categories: [...normalizedCategories, category],
    category,
    created: true,
  };
}