"""Restricted operational admin for the first payroll backend slice."""

from django import forms
from django.contrib import admin, messages
from django.contrib.admin import helpers
from django.core.exceptions import PermissionDenied
from django.db import transaction
from django.db.models import Q
from django.template.response import TemplateResponse

from .enums import ApprovalStatus
from .models import (
    EmployeePayRate,
    FinanceSettings,
    PayrollAuditEvent,
    PayrollDailyWorkEntry,
    PayrollInputLine,
    PayrollPeriod,
    PayrollRun,
    PayrollStatement,
    PayrollStatementAcknowledgement,
    PayrollStatementLine,
    PayrollWorkRecord,
    PayrollWorkSettings,
    VacationPayInstruction,
)
from .payroll.access import has_payroll_permission, has_simple_admin_access
from .payroll.exceptions import PayrollOperationError
from .payroll.services import (
    approve_input_line,
    approve_pay_rate,
    approve_run,
    approve_work_record,
    calculate_period,
    publish_run,
    return_run_for_correction,
    submit_run_for_review,
)


@admin.register(FinanceSettings)
class FinanceSettingsAdmin(admin.ModelAdmin):
    """Singleton allow-list for the native finance management workspace."""

    list_display = ("name", "management_users_count", "updated_at")
    fields = ("name", "management_users", "updated_at")
    readonly_fields = ("updated_at",)
    autocomplete_fields = ("management_users",)

    def has_add_permission(self, request):
        if FinanceSettings.objects.exists():
            return False
        return super().has_add_permission(request)

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser

    @admin.display(description="Доступ к управлению")
    def management_users_count(self, obj):
        count = obj.management_users.count()
        return count or "Все администраторы"


def payroll_reason_action_response(
    model_admin,
    request,
    queryset,
    *,
    action_name,
    title,
    reason_required=True,
    error="",
):
    context = {
        **model_admin.admin_site.each_context(request),
        "title": title,
        "opts": model_admin.model._meta,
        "queryset": queryset,
        "action_name": action_name,
        "action_checkbox_name": helpers.ACTION_CHECKBOX_NAME,
        "reason_required": reason_required,
        "error": error,
    }
    return TemplateResponse(
        request,
        "admin/finance/payroll_reason_action.html",
        context,
    )


def payroll_approval_action_response(
    model_admin,
    request,
    queryset,
    *,
    action_name,
    title,
    error="",
):
    context = {
        **model_admin.admin_site.each_context(request),
        "title": title,
        "opts": model_admin.model._meta,
        "queryset": queryset,
        "action_name": action_name,
        "action_checkbox_name": helpers.ACTION_CHECKBOX_NAME,
        "error": error,
    }
    return TemplateResponse(
        request,
        "admin/finance/payroll_approval_action.html",
        context,
    )


class VersionedDraftAdminForm(forms.ModelForm):
    """Carry the version seen on GET back to the locked admin POST."""

    expected_lock_version = forms.IntegerField(
        min_value=0,
        required=False,
        widget=forms.HiddenInput,
    )

    class Meta:
        fields = "__all__"

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if not self.is_bound and self.instance and self.instance.pk:
            self.initial["expected_lock_version"] = self.instance.lock_version


class PayrollSensitiveAdminMixin:
    """Use explicit payroll roles instead of generic Django model access."""

    view_permissions = ()

    def _has_payroll_access(self, request):
        if request.user.is_superuser:
            return True
        return any(
            has_payroll_permission(request.user, permission)
            for permission in self.view_permissions
        )

    def has_module_permission(self, request):
        return self._has_payroll_access(request)

    def has_view_permission(self, request, obj=None):
        return self._has_payroll_access(request)


class ImmutableApprovedAdminMixin(PayrollSensitiveAdminMixin):
    """Prevent editing approved/voided inputs through Django admin."""

    view_permissions = (
        "finance.manage_payroll_inputs",
        "finance.approve_payroll_inputs",
        "finance.view_all_payroll",
    )
    form = VersionedDraftAdminForm

    def get_readonly_fields(self, request, obj=None):
        readonly = list(super().get_readonly_fields(request, obj))
        if "lock_version" not in readonly:
            readonly.append("lock_version")
        if "status" not in readonly:
            readonly.append("status")
        if obj is not None and (
            not has_payroll_permission(
                request.user,
                "finance.manage_payroll_inputs",
            )
            or obj.status != ApprovalStatus.DRAFT
            or (
                obj.created_by_id != request.user.pk
                and not has_simple_admin_access(request.user)
            )
        ):
            readonly.extend(
                field.name
                for field in obj._meta.concrete_fields
                if field.name not in readonly
            )
        return readonly

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser

    def has_add_permission(self, request):
        return has_payroll_permission(
            request.user,
            "finance.manage_payroll_inputs",
        )

    def has_change_permission(self, request, obj=None):
        return self._has_payroll_access(request)

    @transaction.atomic
    def save_model(self, request, obj, form, change):
        if not has_payroll_permission(
            request.user,
            "finance.manage_payroll_inputs",
        ):
            raise PermissionDenied("Нет права изменять входные данные зарплаты.")
        if change:
            if form is None or form.cleaned_data.get("expected_lock_version") is None:
                raise PermissionDenied(
                    "Версия открытого черновика потеряна; обновите страницу."
                )
            expected_lock_version = form.cleaned_data["expected_lock_version"]
            current = obj.__class__.objects.select_for_update().get(pk=obj.pk)
            if current.status != ApprovalStatus.DRAFT or (
                current.created_by_id != request.user.pk
                and not has_simple_admin_access(request.user)
            ):
                raise PermissionDenied("Этот черновик нельзя изменить.")
            if current.lock_version != expected_lock_version:
                raise PermissionDenied(
                    "Черновик уже изменён другой операцией; обновите страницу."
                )
            obj.status = current.status
            obj.lock_version = current.lock_version
            obj._expected_lock_version = expected_lock_version
        if not change:
            obj.created_by = request.user
        super().save_model(request, obj, form, change)


@admin.register(PayrollPeriod)
class PayrollPeriodAdmin(PayrollSensitiveAdminMixin, admin.ModelAdmin):
    view_permissions = (
        "finance.manage_payroll_inputs",
        "finance.calculate_payroll",
        "finance.approve_payroll",
        "finance.publish_payroll",
        "finance.view_all_payroll",
    )
    list_display = [
        "code",
        "name",
        "date_from",
        "date_to",
        "status",
        "current_run",
    ]
    list_filter = ["status", "currency"]
    search_fields = ["code", "name"]
    readonly_fields = [
        "status",
        "current_run",
        "lock_version",
        "created_by",
        "created_at",
        "updated_at",
    ]
    actions = ["calculate_selected"]

    def save_model(self, request, obj, form, change):
        if not change:
            obj.created_by = request.user
        super().save_model(request, obj, form, change)

    def has_add_permission(self, request):
        return has_payroll_permission(
            request.user,
            "finance.manage_payroll_inputs",
        )

    def has_change_permission(self, request, obj=None):
        if obj is None:
            return self._has_payroll_access(request)
        return has_payroll_permission(
            request.user,
            "finance.manage_payroll_inputs",
        )

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser

    @admin.action(description="Рассчитать выбранные периоды")
    def calculate_selected(self, request, queryset):
        if not has_payroll_permission(request.user, "finance.calculate_payroll"):
            self.message_user(request, "Недостаточно прав.", level=messages.ERROR)
            return
        reason_required = any(period.current_run_id for period in queryset)
        if "confirm_payroll_action" not in request.POST:
            return payroll_reason_action_response(
                self,
                request,
                queryset,
                action_name="calculate_selected",
                title="Расчёт зарплатного периода",
                reason_required=reason_required,
            )
        reason = request.POST.get("reason", "").strip()
        if reason_required and not reason:
            return payroll_reason_action_response(
                self,
                request,
                queryset,
                action_name="calculate_selected",
                title="Расчёт зарплатного периода",
                reason_required=True,
                error="Для повторного расчёта обязательно укажите основание.",
            )
        success_count = 0
        for period in queryset:
            try:
                calculate_period(
                    period.pk,
                    actor=request.user,
                    recalculation_reason=reason if period.current_run_id else "",
                )
            except PayrollOperationError as exc:
                self.message_user(
                    request,
                    f"{period}: {exc.message} ({exc.code})",
                    level=messages.ERROR,
                )
            else:
                success_count += 1
        if success_count:
            self.message_user(
                request,
                f"Рассчитано периодов: {success_count}",
                level=messages.SUCCESS,
            )


@admin.register(EmployeePayRate)
class EmployeePayRateAdmin(ImmutableApprovedAdminMixin, admin.ModelAdmin):
    exclude = ["self_approval_overridden"]
    list_display = [
        "employee",
        "rate_code",
        "amount",
        "currency",
        "effective_from",
        "revision",
        "status",
    ]
    list_filter = [
        "status",
        "currency",
        "source",
        "effective_from",
    ]
    search_fields = [
        "employee__last_name",
        "employee__first_name",
        "employee__email",
        "rate_code",
        "source_ref",
    ]
    readonly_fields = [
        "created_by",
        "created_at",
        "updated_at",
        "approved_by",
        "approved_at",
        "voided_by",
        "voided_at",
    ]
    actions = ["approve_selected"]

    @staticmethod
    def _revision_chain_ids(records):
        chain_ids = {record.pk for record in records if record.pk is not None}
        frontier = set(chain_ids)
        while frontier:
            linked_rows = EmployeePayRate.objects.filter(
                Q(pk__in=frontier) | Q(replaces_id__in=frontier)
            ).values_list("pk", "replaces_id")
            linked_ids = {
                linked_id
                for row in linked_rows
                for linked_id in row
                if linked_id is not None
            }
            frontier = linked_ids - chain_ids
            chain_ids.update(frontier)
        return chain_ids

    def get_deleted_objects(self, objs, request):
        chain_ids = self._revision_chain_ids(objs)
        records = EmployeePayRate.objects.filter(pk__in=chain_ids).order_by(
            "employee_id",
            "effective_from",
            "revision",
            "pk",
        )
        deleted_objects = [
            (
                f"{self.model._meta.verbose_name}: {record} "
                f"(ID {record.pk}, ревизия {record.revision}, "
                f"статус: {record.get_status_display()})"
            )
            for record in records
        ]
        return (
            deleted_objects,
            {self.model._meta.verbose_name_plural: len(deleted_objects)},
            set(),
            [],
        )

    @transaction.atomic
    def _delete_revision_chains(self, records):
        chain_ids = self._revision_chain_ids(records)
        revisions = (
            EmployeePayRate.objects.select_for_update()
            .filter(pk__in=chain_ids)
            .order_by("-revision", "-pk")
        )
        for revision in revisions:
            revision.delete()

    def delete_model(self, request, obj):
        self._delete_revision_chains([obj])

    def delete_queryset(self, request, queryset):
        self._delete_revision_chains(queryset)

    @admin.action(description="Утвердить выбранные ставки")
    def approve_selected(self, request, queryset):
        return self._approve_records(
            request,
            queryset,
            approve_pay_rate,
            action_name="approve_selected",
            title="Утверждение ставок",
        )

    def _approve_records(
        self,
        request,
        queryset,
        service,
        *,
        action_name,
        title,
    ):
        if not has_payroll_permission(
            request.user,
            "finance.approve_payroll_inputs",
        ):
            self.message_user(request, "Недостаточно прав.", level=messages.ERROR)
            return
        if "confirm_payroll_approval" not in request.POST:
            return payroll_approval_action_response(
                self,
                request,
                queryset,
                action_name=action_name,
                title=title,
            )
        for record in queryset:
            try:
                expected_lock_version = int(request.POST[f"lock_version_{record.pk}"])
            except (KeyError, TypeError, ValueError):
                return payroll_approval_action_response(
                    self,
                    request,
                    queryset,
                    action_name=action_name,
                    title=title,
                    error="Версия черновика потеряна; проверьте данные ещё раз.",
                )
            try:
                service(
                    record.pk,
                    actor=request.user,
                    expected_lock_version=expected_lock_version,
                )
            except PayrollOperationError as exc:
                self.message_user(
                    request,
                    f"{record}: {exc.message} ({exc.code})",
                    level=messages.ERROR,
                )


@admin.register(PayrollWorkRecord)
class PayrollWorkRecordAdmin(ImmutableApprovedAdminMixin, admin.ModelAdmin):
    exclude = ["self_approval_overridden"]
    list_display = [
        "period",
        "employee",
        "target_points",
        "actual_points",
        "revision",
        "status",
    ]
    list_filter = ["period", "status", "source"]
    search_fields = [
        "employee__last_name",
        "employee__first_name",
        "employee__email",
        "source_ref",
    ]
    readonly_fields = [
        "created_by",
        "created_at",
        "updated_at",
        "approved_by",
        "approved_at",
        "voided_by",
        "voided_at",
    ]
    actions = ["approve_selected"]

    @admin.action(description="Утвердить выбранную выработку")
    def approve_selected(self, request, queryset):
        return EmployeePayRateAdmin._approve_records(
            self,
            request,
            queryset,
            approve_work_record,
            action_name="approve_selected",
            title="Утверждение выработки",
        )


@admin.register(PayrollDailyWorkEntry)
class PayrollDailyWorkEntryAdmin(admin.ModelAdmin):
    list_display = [
        "work_date",
        "employee",
        "target_points",
        "actual_points",
        "period",
        "updated_at",
    ]
    list_filter = ["period", "work_date"]
    search_fields = [
        "employee__last_name",
        "employee__first_name",
        "employee__email",
        "note",
    ]
    readonly_fields = ["lock_version", "created_at", "updated_at"]


@admin.register(PayrollWorkSettings)
class PayrollWorkSettingsAdmin(admin.ModelAdmin):
    fields = ["daily_target_points", "updated_at"]
    list_display = ["daily_target_points", "updated_at"]
    readonly_fields = ["updated_at"]

    def has_add_permission(self, request):
        if PayrollWorkSettings.objects.exists():
            return False
        return super().has_add_permission(request)

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser


@admin.register(PayrollInputLine)
class PayrollInputLineAdmin(ImmutableApprovedAdminMixin, admin.ModelAdmin):
    exclude = ["reversal_of", "self_approval_overridden"]
    list_display = [
        "period",
        "employee",
        "component_code",
        "amount",
        "relates_to_period",
        "status",
    ]
    list_filter = [
        "period",
        "status",
        "component_code",
        "source",
    ]
    search_fields = [
        "employee__last_name",
        "employee__first_name",
        "employee__email",
        "reason",
        "source_ref",
    ]
    readonly_fields = [
        "idempotency_key",
        "created_by",
        "created_at",
        "approved_by",
        "approved_at",
        "voided_by",
        "voided_at",
    ]
    actions = ["approve_selected"]

    @admin.action(description="Утвердить выбранные строки")
    def approve_selected(self, request, queryset):
        return EmployeePayRateAdmin._approve_records(
            self,
            request,
            queryset,
            approve_input_line,
            action_name="approve_selected",
            title="Утверждение начислений и удержаний",
        )


@admin.register(VacationPayInstruction)
class VacationPayInstructionAdmin(admin.ModelAdmin):
    list_display = (
        "vacation_terms",
        "paid_days",
        "period",
        "amount",
        "status",
        "created_at",
    )
    list_filter = ("status", "period")
    search_fields = (
        "vacation_terms__request__employee__last_name",
        "vacation_terms__request__employee__first_name",
        "vacation_terms__request__employee__email",
    )
    autocomplete_fields = (
        "vacation_terms",
        "period",
        "payroll_input_line",
        "created_by",
    )
    readonly_fields = ("created_at", "updated_at")


class PayrollStatementLineInline(admin.TabularInline):
    model = PayrollStatementLine
    extra = 0
    can_delete = False
    fields = ["position", "code", "label", "kind", "amount", "reason"]
    readonly_fields = fields

    def has_add_permission(self, request, obj=None):
        return request.user.is_superuser

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser


@admin.register(PayrollRun)
class PayrollRunAdmin(PayrollSensitiveAdminMixin, admin.ModelAdmin):
    exclude = ["self_approval_overridden"]
    view_permissions = (
        "finance.calculate_payroll",
        "finance.approve_payroll",
        "finance.publish_payroll",
        "finance.view_all_payroll",
    )
    list_display = [
        "period",
        "revision",
        "status",
        "employee_count",
        "gross_total",
        "payable_total",
        "requested_by",
    ]
    list_filter = ["status", "period"]
    search_fields = ["period__code", "input_hash", "result_hash"]
    readonly_fields = [
        field.name
        for field in PayrollRun._meta.concrete_fields
        if field.name != "self_approval_overridden"
    ]
    actions = [
        "request_review",
        "return_selected",
        "approve_selected",
        "publish_selected",
    ]

    def has_add_permission(self, request):
        return request.user.is_superuser

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser

    def has_change_permission(self, request, obj=None):
        return self._has_payroll_access(request)

    def _run_action(self, request, queryset, service):
        for run in queryset:
            try:
                service(run.pk, actor=request.user)
            except PayrollOperationError as exc:
                self.message_user(
                    request,
                    f"{run}: {exc.message} ({exc.code})",
                    level=messages.ERROR,
                )

    @admin.action(description="Передать на проверку")
    def request_review(self, request, queryset):
        self._run_action(request, queryset, submit_run_for_review)

    @admin.action(description="Вернуть расчёт на исправление")
    def return_selected(self, request, queryset):
        if "confirm_payroll_action" not in request.POST:
            return payroll_reason_action_response(
                self,
                request,
                queryset,
                action_name="return_selected",
                title="Возврат расчёта на исправление",
            )
        reason = request.POST.get("reason", "").strip()
        if not reason:
            return payroll_reason_action_response(
                self,
                request,
                queryset,
                action_name="return_selected",
                title="Возврат расчёта на исправление",
                error="Укажите причину возврата.",
            )
        for run in queryset:
            try:
                return_run_for_correction(
                    run.pk,
                    actor=request.user,
                    reason=reason,
                )
            except PayrollOperationError as exc:
                self.message_user(
                    request,
                    f"{run}: {exc.message} ({exc.code})",
                    level=messages.ERROR,
                )

    @admin.action(description="Утвердить расчёт")
    def approve_selected(self, request, queryset):
        self._run_action(request, queryset, approve_run)

    @admin.action(description="Опубликовать расчётные листки")
    def publish_selected(self, request, queryset):
        self._run_action(request, queryset, publish_run)


@admin.register(PayrollStatement)
class PayrollStatementAdmin(PayrollSensitiveAdminMixin, admin.ModelAdmin):
    view_permissions = ("finance.view_all_payroll",)
    list_display = [
        "run",
        "employee",
        "gross_total",
        "deduction_total",
        "payment_total",
        "opening_balance",
        "closing_balance",
        "payable",
    ]
    list_filter = ["run__period", "run__status", "currency"]
    search_fields = [
        "employee__last_name",
        "employee__first_name",
        "employee__email",
        "result_hash",
    ]
    readonly_fields = [field.name for field in PayrollStatement._meta.concrete_fields]
    inlines = [PayrollStatementLineInline]

    def has_add_permission(self, request):
        return request.user.is_superuser

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser

    def has_change_permission(self, request, obj=None):
        return self._has_payroll_access(request)


@admin.register(PayrollStatementAcknowledgement)
class PayrollStatementAcknowledgementAdmin(
    PayrollSensitiveAdminMixin,
    admin.ModelAdmin,
):
    view_permissions = (
        "finance.view_all_payroll",
        "finance.audit_payroll",
    )
    list_display = [
        "statement",
        "employee",
        "viewed_at",
        "acknowledged_at",
        "disputed_at",
    ]
    list_filter = ["acknowledged_at", "disputed_at"]
    search_fields = [
        "employee__last_name",
        "employee__first_name",
        "statement__result_hash",
    ]
    readonly_fields = [
        field.name for field in PayrollStatementAcknowledgement._meta.concrete_fields
    ]

    def has_add_permission(self, request):
        return request.user.is_superuser

    def has_change_permission(self, request, obj=None):
        return self._has_payroll_access(request)

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser


@admin.register(PayrollAuditEvent)
class PayrollAuditEventAdmin(PayrollSensitiveAdminMixin, admin.ModelAdmin):
    view_permissions = ("finance.audit_payroll",)
    list_display = [
        "created_at",
        "actor",
        "action",
        "object_type",
        "object_id",
        "period",
    ]
    list_filter = ["action", "object_type", "period"]
    search_fields = ["object_id", "before_hash", "after_hash"]
    readonly_fields = [field.name for field in PayrollAuditEvent._meta.concrete_fields]

    def has_add_permission(self, request):
        return request.user.is_superuser

    def has_change_permission(self, request, obj=None):
        return has_payroll_permission(request.user, "finance.audit_payroll")

    def has_delete_permission(self, request, obj=None):
        return request.user.is_superuser