import { apiClient } from '../shared/api-client.js';

export const SUBJECT_TABLE_COLUMNS = 6;
export const SUBJECT_PAGE_SIZES = [25, 50, 100];

export const SUBJECT_SORT_OPTIONS = Object.freeze([
    { value: 'name,asc', label: 'По названию А–Я' },
    { value: 'name,desc', label: 'По названию Я–А' },
    { value: 'code,asc', label: 'По коду' },
    { value: 'departmentId,asc', label: 'По кафедре' }
]);

const DEFAULT_STATE = Object.freeze({
    query: '',
    departmentId: '',
    page: 0,
    size: 25,
    sort: 'name,asc'
});

export function normalizeSubjectsState(restored = {}) {
    const size = Number(restored.subjectSize);
    return {
        query: restored.subjectQuery || '',
        departmentId: restored.subjectDepartment || '',
        page: Math.max(Number(restored.subjectPage) || 0, 0),
        size: SUBJECT_PAGE_SIZES.includes(size) ? size : 25,
        sort: SUBJECT_SORT_OPTIONS.some(option => option.value === restored.subjectSort)
            ? restored.subjectSort
            : 'name,asc'
    };
}

export function initialSubjectsState(restored = {}) {
    return normalizeSubjectsState(restored);
}

export function defaultSubjectsState() {
    return { ...DEFAULT_STATE };
}

export function subjectsQueryParams(state) {
    const [sort, direction] = String(state.sort || 'name,asc').split(',');
    const params = new URLSearchParams({
        query: state.query || '',
        page: String(state.page || 0),
        size: String(state.size || 25),
        sort,
        direction
    });
    if (state.departmentId) params.set('departmentId', state.departmentId);
    return `/api/subjects/page?${params}`;
}

export function subjectsUrlState(state) {
    return {
        subjectQuery: state.query || '',
        subjectDepartment: state.departmentId || '',
        subjectPage: state.page || '',
        subjectSize: state.size === 25 ? '' : state.size,
        subjectSort: state.sort === 'name,asc' ? '' : state.sort
    };
}

export function fetchDepartments(client = apiClient) {
    return client.get('/api/departments', { errorMessage: 'Не удалось загрузить список кафедр' });
}

export function fetchSubjectsPage(state, client = apiClient) {
    return client.get(subjectsQueryParams(state), { errorMessage: 'Не удалось загрузить дисциплины' });
}

export function teacherAssignmentsEndpoint(subjectIds) {
    const params = new URLSearchParams();
    (subjectIds || []).forEach(subjectId => params.append('subjectId', subjectId));
    return `/api/teacher-subjects?${params}`;
}

export function fetchTeacherAssignments(subjectIds, client = apiClient) {
    if (!(subjectIds || []).length) return Promise.resolve([]);
    return client.get(
        teacherAssignmentsEndpoint(subjectIds),
        { errorMessage: 'Не удалось загрузить привязки преподавателей' }
    );
}

export function createSubject({ name, code, departmentId }, client = apiClient) {
    return client.post(
        '/api/subjects',
        { name, code, departmentId: Number(departmentId) },
        { errorMessage: 'Ошибка создания' }
    );
}

export function archiveSubject(id, client = apiClient) {
    return client.delete(`/api/subjects/${id}`, { errorMessage: 'Ошибка архивирования' });
}

export function assignTeacher({ userId, subjectId }, client = apiClient) {
    return client.post(
        '/api/teacher-subjects',
        { userId: Number(userId), subjectId: Number(subjectId) },
        { errorMessage: 'Ошибка привязки' }
    );
}

export function removeTeacherAssignment({ userId, subjectId }, client = apiClient) {
    return client.delete('/api/teacher-subjects', {
        json: { userId: Number(userId), subjectId: Number(subjectId) },
        errorMessage: 'Ошибка удаления привязки'
    });
}

export function teachersSearchEndpoint(query, selectedId) {
    const params = new URLSearchParams({ query, limit: '30' });
    if (selectedId) params.set('selectedId', selectedId);
    return `/api/users/teachers/options?${params}`;
}

export function departmentLabel(departments, departmentId) {
    const department = (departments || []).find(item => String(item.id) === String(departmentId));
    if (!department) return departmentId || '-';
    return department.departmentName || department.name || departmentId;
}

export function departmentOptionLabel(department) {
    const name = department.departmentName || department.name || 'Без названия';
    const code = department.departmentCode || department.code || department.id;
    return `${name} (${code})`;
}

export function groupTeachersBySubject(assignments) {
    const grouped = new Map();
    (assignments || []).forEach(assignment => {
        const key = String(assignment.subjectId);
        if (!grouped.has(key)) grouped.set(key, []);
        grouped.get(key).push(assignment);
    });
    return grouped;
}

export function subjectContextLabel(subject) {
    return `${subject.code ? `${subject.code} · ` : ''}${subject.name}`;
}

export function subjectsEmptyMessage(state) {
    return state.query || state.departmentId ? 'Дисциплины не найдены' : 'Дисциплин пока нет';
}

export function normalizePageState(state, page) {
    const nextPage = Number(page);
    return { ...state, page: Number.isFinite(nextPage) && nextPage > 0 ? nextPage : 0 };
}