import { apiClient } from '../shared/api-client.js';
import {
    addDays,
    formatDate,
    formatDateShort,
    parseIsoDate,
    toIsoDate,
    trimTime
} from './schedule-view-service.js';

// Волна 6 (этап 5): чистая логика и контракты API разовых правок расписания,
// перенесённые из legacy admin/js/views/schedule-override-panel.js без изменения
// поведения. Императивный модуль панели заменён React-состоянием во вкладке
// просмотра расписаний.

export const OVERRIDE_EDIT_ROLES = new Set(['ADMIN', 'EDUCATION_OFFICE']);

export const OVERRIDE_ACTION_LABELS = {
    MOVE: 'Перенос',
    REPLACE: 'Замена',
    CANCEL: 'Отмена'
};

export const OVERRIDE_DAY_LABELS = ['Пн', 'Вт', 'Ср', 'Чт', 'Пт', 'Сб', 'Вс'];

export const OVERRIDE_MONTH_LABELS = [
    'Январь', 'Февраль', 'Март', 'Апрель', 'Май', 'Июнь',
    'Июль', 'Август', 'Сентябрь', 'Октябрь', 'Ноябрь', 'Декабрь'
];

// --- Права и решения ---

export function canEditScheduleOverrides(role) {
    return OVERRIDE_EDIT_ROLES.has(role);
}

export function overrideActionForChanges(changes) {
    if (changes.dateChanged || changes.timeChanged) return 'MOVE';
    if (changes.teacherChanged || changes.classroomChanged || changes.formatChanged) return 'REPLACE';
    return null;
}

// --- Даты и время ---

export function weekDates(value) {
    const selected = parseIsoDate(value);
    const day = selected.getDay() || 7;
    const monday = addDays(selected, 1 - day);
    return Array.from({ length: 7 }, (_, index) => toIsoDate(addDays(monday, index)));
}

export function pickMatchingTimeSlot(slots, preferredId, startTime, endTime) {
    const safeSlots = Array.isArray(slots) ? slots : [];
    const byId = preferredId == null
        ? null
        : safeSlots.find(slot => String(slot.id) === String(preferredId));
    if (byId) return byId;
    const normalizedStart = trimTime(startTime);
    const normalizedEnd = trimTime(endTime);
    if (!normalizedStart || !normalizedEnd) return null;
    return safeSlots.find(slot => trimTime(slot.startTime) === normalizedStart
        && trimTime(slot.endTime) === normalizedEnd) || null;
}

export function overrideIntervalLabel(start, end) {
    return `${trimTime(start)}–${trimTime(end)}`;
}

export function overrideTimeSlotLabel(slot) {
    const order = slot.orderNumber ? `${slot.orderNumber} пара · ` : '';
    return `${order}${overrideIntervalLabel(slot.startTime, slot.endTime)}`;
}

// --- Источник правки ---

export function overrideSourceFrom(lesson, existing) {
    return {
        baseRuleSlotId: lesson.scheduleRuleSlotId,
        lessonDate: lesson.originalLessonDate || existing?.lessonDate || lesson.date,
        subjectName: existing?.subjectName || lesson.subjectName || 'Без дисциплины',
        lessonTypeName: existing?.lessonTypeName || lesson.lessonTypeName || 'Тип не указан',
        groupNames: existing?.groupNames?.length ? existing.groupNames : (lesson.groupNames || []),
        timeSlotId: existing?.sourceTimeSlotId || lesson.timeSlotId,
        timeSlotOrder: existing?.sourceTimeSlotOrder || lesson.timeSlotOrder,
        startTime: existing?.sourceStartTime || lesson.startTime,
        endTime: existing?.sourceEndTime || lesson.endTime,
        teacherId: existing?.sourceTeacherId || lesson.teacherId,
        teacherName: existing?.sourceTeacherName || lesson.teacherName,
        classroomId: existing?.sourceClassroomId || lesson.classroomId,
        classroomName: existing?.sourceClassroomName || lesson.classroomName,
        lessonFormat: existing?.sourceLessonFormat || lesson.lessonFormat || 'Очно'
    };
}

export function initialTimePreference(existing, source) {
    return {
        id: existing?.newTimeSlotId || source.timeSlotId,
        startTime: existing?.newTimeSlotId ? null : source.startTime,
        endTime: existing?.newTimeSlotId ? null : source.endTime
    };
}

// Синтетическое занятие для открытия существующей правки из реестра.
export function lessonFromOverride(override, dictionaries) {
    return {
        scheduleRuleSlotId: override.baseRuleSlotId,
        date: override.targetLessonDate || override.lessonDate,
        originalLessonDate: override.lessonDate,
        scheduleOverrideId: override.id,
        subjectName: override.subjectName,
        lessonTypeName: override.lessonTypeName,
        groupNames: override.groupNames,
        timeSlotId: override.newTimeSlotId || override.sourceTimeSlotId,
        timeSlotOrder: override.sourceTimeSlotOrder,
        startTime: override.sourceStartTime,
        endTime: override.sourceEndTime,
        teacherId: override.newTeacherId || override.sourceTeacherId,
        teacherName: overrideTeacherName(dictionaries, override.newTeacherId) || override.sourceTeacherName,
        classroomId: override.newClassroomId || override.sourceClassroomId,
        classroomName: overrideClassroomName(dictionaries, override.newClassroomId) || override.sourceClassroomName,
        lessonFormat: override.newLessonFormat || override.sourceLessonFormat
    };
}

export function overrideTeacherName(dictionaries, id) {
    if (id == null || id === '') return '';
    const teacher = (dictionaries.teachers || []).find(item => String(item.id) === String(id));
    return teacher?.fullName || teacher?.username || '';
}

export function overrideClassroomName(dictionaries, id) {
    if (id == null || id === '') return '';
    const classroom = (dictionaries.classrooms || []).find(item => String(item.id) === String(id));
    return classroom ? classroomOptionLabel(classroom) : '';
}

export function classroomOptionLabel(room) {
    return room?.name || '';
}

// --- Сравнение «было / станет» ---

export function overrideBeforeMeta(source) {
    return [
        formatDate(source.lessonDate),
        overrideIntervalLabel(source.startTime, source.endTime),
        source.teacherName,
        source.classroomName,
        source.lessonFormat,
        source.groupNames.join(', ')
    ].filter(Boolean).join(' · ');
}

export function overrideAfterMeta({ source, targetDate, selectedTime, teacherName, classroomName, lessonFormat }) {
    return [
        formatDate(targetDate),
        selectedTime ? overrideIntervalLabel(selectedTime.startTime, selectedTime.endTime) : 'Время не выбрано',
        teacherName,
        classroomName,
        lessonFormat,
        source.groupNames.join(', ')
    ].filter(Boolean).join(' · ');
}

// --- Календарь семестра ---

export function semesterCalendarMonths(startDate, endDate, available, selectedDate) {
    if (!startDate || !endDate) return [];
    const start = parseIsoDate(startDate);
    const end = parseIsoDate(endDate);
    const months = [];
    for (let cursor = new Date(start.getFullYear(), start.getMonth(), 1);
         cursor <= end;
         cursor = new Date(cursor.getFullYear(), cursor.getMonth() + 1, 1)) {
        months.push(overrideMonth(cursor, startDate, endDate, available, selectedDate));
    }
    return months;
}

function overrideMonth(month, semesterStart, semesterEnd, available, selectedDate) {
    const year = month.getFullYear();
    const monthIndex = month.getMonth();
    const firstDay = new Date(year, monthIndex, 1).getDay() || 7;
    const dayCount = new Date(year, monthIndex + 1, 0).getDate();
    const blanks = Array.from({ length: firstDay - 1 }, (_, index) => ({ blank: true, key: `blank-${index}` }));
    const days = Array.from({ length: dayCount }, (_, index) => {
        const date = toIsoDate(new Date(year, monthIndex, index + 1));
        const enabled = date >= semesterStart && date <= semesterEnd && available.has(date);
        return {
            key: date,
            date,
            day: index + 1,
            enabled,
            active: date === selectedDate
        };
    });
    return {
        title: `${OVERRIDE_MONTH_LABELS[monthIndex]} ${year}`,
        blanks,
        days
    };
}

// --- Payload правки ---

export function buildOverridePayload({
    source,
    selectedOverride,
    targetDate,
    timeSlotId,
    teacherId,
    classroomId,
    lessonFormat,
    comment
}) {
    if (!timeSlotId) {
        return { error: 'Выберите время занятия для выбранной даты' };
    }
    const dateChanged = targetDate !== source.lessonDate;
    const timeChanged = String(timeSlotId) !== String(source.timeSlotId);
    const teacherChanged = String(teacherId) !== String(source.teacherId);
    const classroomChanged = String(classroomId) !== String(source.classroomId);
    const formatChanged = lessonFormat !== source.lessonFormat;
    const action = overrideActionForChanges({
        dateChanged,
        timeChanged,
        teacherChanged,
        classroomChanged,
        formatChanged
    });
    if (!action) {
        return {
            error: selectedOverride
                ? 'Параметры совпадают с правилом. Используйте «Вернуть по правилу»'
                : 'Измените дату, время, преподавателя, аудиторию или формат'
        };
    }
    return {
        payload: {
            baseRuleSlotId: source.baseRuleSlotId,
            lessonDate: source.lessonDate,
            targetLessonDate: dateChanged ? targetDate : null,
            action,
            newTimeSlotId: (dateChanged || timeChanged) ? Number(timeSlotId) : null,
            newTeacherId: teacherChanged ? Number(teacherId) : null,
            newClassroomId: classroomChanged ? Number(classroomId) : null,
            newLessonFormat: formatChanged ? lessonFormat : null,
            comment: comment.trim() || null
        }
    };
}

export function buildCancelOverridePayload(source, comment) {
    return {
        baseRuleSlotId: source.baseRuleSlotId,
        lessonDate: source.lessonDate,
        targetLessonDate: null,
        action: 'CANCEL',
        newTimeSlotId: null,
        newTeacherId: null,
        newClassroomId: null,
        newLessonFormat: null,
        comment: comment.trim() || null
    };
}

// --- Реестр правок ---

export function overrideRegistryItem(override, dictionaries) {
    const target = override.targetLessonDate
        ? ` → ${formatDate(override.targetLessonDate)}`
        : '';
    const result = override.action === 'CANCEL'
        ? 'Занятие отменено'
        : [
            override.newTimeSlotId ? `слот ${override.newTimeSlotId}` : null,
            overrideTeacherName(dictionaries, override.newTeacherId),
            overrideClassroomName(dictionaries, override.newClassroomId),
            override.newLessonFormat
        ].filter(Boolean).join(' · ');
    return {
        id: override.id,
        actionLabel: OVERRIDE_ACTION_LABELS[override.action] || override.action,
        actionClass: `action-${String(override.action).toLowerCase()}`,
        timeText: `${formatDate(override.lessonDate)}${target}`,
        subject: override.subjectName || 'Занятие',
        description: [
            override.lessonTypeName,
            (override.groupNames || []).join(', '),
            result || 'Параметры изменены'
        ].filter(Boolean).join(' · '),
        comment: override.comment || ''
    };
}

// --- Контракты API ---

export function overrideAvailabilityEndpoint(baseRuleSlotId, lessonDate) {
    return `/api/edu-office/schedule/overrides/availability?baseRuleSlotId=${encodeURIComponent(baseRuleSlotId)}`
        + `&lessonDate=${encodeURIComponent(lessonDate)}`;
}

export async function fetchOverrideAvailability(baseRuleSlotId, lessonDate, client = apiClient) {
    return client.get(overrideAvailabilityEndpoint(baseRuleSlotId, lessonDate), {
        errorMessage: 'Не удалось загрузить доступные даты занятия'
    });
}

export function effectiveTimeSlotsEndpoint(date) {
    return `/api/admin/time-slots/effective?date=${encodeURIComponent(date)}`;
}

export async function fetchEffectiveTimeSlots(date, client = apiClient) {
    return client.get(effectiveTimeSlotsEndpoint(date), {
        errorMessage: 'Не удалось загрузить время занятий'
    });
}

export async function saveScheduleOverride(payload, overrideId, client = apiClient) {
    return overrideId
        ? client.put(`/api/edu-office/schedule/overrides/${encodeURIComponent(overrideId)}`, payload, {
            errorMessage: 'Не удалось сохранить разовое изменение'
        })
        : client.post('/api/edu-office/schedule/overrides', payload, {
            errorMessage: 'Не удалось сохранить разовое изменение'
        });
}

export async function deleteScheduleOverride(overrideId, client = apiClient) {
    return client.delete(`/api/edu-office/schedule/overrides/${encodeURIComponent(overrideId)}`, {
        errorMessage: 'Не удалось удалить разовое изменение'
    });
}