"""
Unit-Tests für mailmerge.services.retention.

Decken ab:
- Stichtag-Berechnung (inkl. Edge Cases days < 1)
- QuerySet-Logik (welche Jobs sind Kandidaten?)
- Bulk-Cleanup mit Dry-Run
- File-Löschung wird ausgelöst
- Wartende/laufende Jobs werden NICHT gelöscht
- finished_at-Fallback auf created_at
"""
from __future__ import annotations

from datetime import timedelta
from unittest.mock import patch

import pytest
from django.core.files.base import ContentFile
from django.utils import timezone

from mailmerge.models import JobLogEntry, LetterTemplate, MailMergeJob
from mailmerge.services.retention import (
    CleanupResult,
    cleanup_expired_jobs,
    expired_jobs_queryset,
    get_cutoff,
)


pytestmark = pytest.mark.django_db


# ---------------------------------------------------------------------------
# Fixtures
# ---------------------------------------------------------------------------

@pytest.fixture
def template(user):
    return LetterTemplate.objects.create(
        name="Retention-Testvorlage",
        file=ContentFile(b"dummy-docx", name="tpl.docx"),
        placeholders=["vorname"],
        created_by=user,
    )


def _make_job(template, user, *, status, finished_offset_days=None,
              created_offset_days=0, with_files=False):
    """Hilfsfunktion zum Anlegen eines Jobs mit künstlichem Zeitstempel.

    finished_offset_days: positive Zahl = vor X Tagen abgeschlossen.
    None = finished_at bleibt NULL (Fallback-Test).

    Reihenfolge wichtig: Files MUSS vor dem Zurückdatieren der Timestamps
    angehängt werden, weil `FileField.save(save=True)` ein `instance.save()`
    triggert, das die per `.update()` gesetzten Datumswerte wieder mit den
    aktuellen Memory-Werten überschreibt.
    """
    now = timezone.now()
    job = MailMergeJob.objects.create(
        template=template,
        recipients_csv=ContentFile(b"vorname\nAnna\n", name="r.csv"),
        status=status,
        created_by=user,
    )
    if with_files:
        # save=False, damit kein zusätzliches instance.save() die
        # Zeitstempel verbiegt. Die Datei landet trotzdem auf dem Storage.
        job.result_pdf.save("out.pdf", ContentFile(b"%PDF-1.4"), save=False)
        job.save(update_fields=["result_pdf"])

    # Jetzt erst die Timestamps zurückdatieren — über `.update()`, damit
    # auto_now_add nicht greift und kein zusätzliches .save() ausgelöst wird.
    new_created = now - timedelta(days=created_offset_days)
    new_finished = (
        now - timedelta(days=finished_offset_days)
        if finished_offset_days is not None else None
    )
    MailMergeJob.objects.filter(pk=job.pk).update(
        created_at=new_created,
        finished_at=new_finished,
    )
    job.refresh_from_db()
    return job


# ---------------------------------------------------------------------------
# get_cutoff
# ---------------------------------------------------------------------------

class TestGetCutoff:
    def test_uses_settings_default(self, settings):
        settings.JOB_RETENTION_DAYS = 30
        cutoff = get_cutoff()
        delta = timezone.now() - cutoff
        # Toleranz, weil ein paar Millisekunden zwischen den Aufrufen liegen
        assert timedelta(days=29, hours=23) < delta < timedelta(days=30, hours=1)

    def test_explicit_overrides_settings(self, settings):
        settings.JOB_RETENTION_DAYS = 30
        cutoff = get_cutoff(retention_days=7)
        delta = timezone.now() - cutoff
        assert timedelta(days=6, hours=23) < delta < timedelta(days=7, hours=1)

    def test_zero_raises(self):
        with pytest.raises(ValueError):
            get_cutoff(retention_days=0)

    def test_negative_raises(self):
        with pytest.raises(ValueError):
            get_cutoff(retention_days=-5)


# ---------------------------------------------------------------------------
# expired_jobs_queryset
# ---------------------------------------------------------------------------

class TestExpiredJobsQueryset:
    def test_done_job_older_than_cutoff_is_candidate(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=40)
        cutoff = timezone.now() - timedelta(days=30)
        assert expired_jobs_queryset(cutoff).count() == 1

    def test_done_job_younger_than_cutoff_is_not_candidate(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=10)
        cutoff = timezone.now() - timedelta(days=30)
        assert expired_jobs_queryset(cutoff).count() == 0

    def test_failed_jobs_are_candidates(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.FAILED,
                  finished_offset_days=40)
        cutoff = timezone.now() - timedelta(days=30)
        assert expired_jobs_queryset(cutoff).count() == 1

    def test_running_jobs_are_never_candidates(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.RUNNING,
                  finished_offset_days=None, created_offset_days=999)
        cutoff = timezone.now() - timedelta(days=30)
        assert expired_jobs_queryset(cutoff).count() == 0

    def test_pending_jobs_are_never_candidates(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.PENDING,
                  finished_offset_days=None, created_offset_days=999)
        cutoff = timezone.now() - timedelta(days=30)
        assert expired_jobs_queryset(cutoff).count() == 0

    def test_finished_at_null_falls_back_to_created_at(self, template, user):
        """Job ohne finished_at, aber created_at > cutoff → muss matchen.

        Schützt vor verwaisten 'DONE'-Jobs, bei denen aus irgendeinem Grund
        finished_at fehlt (z.B. Crash zwischen save() und finished_at).
        """
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=None, created_offset_days=40)
        cutoff = timezone.now() - timedelta(days=30)
        assert expired_jobs_queryset(cutoff).count() == 1


# ---------------------------------------------------------------------------
# cleanup_expired_jobs
# ---------------------------------------------------------------------------

class TestCleanupHappyPath:
    def test_deletes_expired_done_job(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=40)
        result = cleanup_expired_jobs(retention_days=30)
        assert result.deleted_jobs == 1
        assert MailMergeJob.objects.count() == 0

    def test_keeps_recent_job(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=10)
        result = cleanup_expired_jobs(retention_days=30)
        assert result.deleted_jobs == 0
        assert MailMergeJob.objects.count() == 1

    def test_deletes_associated_files(self, template, user):
        job = _make_job(template, user, status=MailMergeJob.Status.DONE,
                        finished_offset_days=40, with_files=True)
        # Eingangs-CSV + Output-PDF = 2 Dateien
        assert job.recipients_csv.name
        assert job.result_pdf.name
        result = cleanup_expired_jobs(retention_days=30)
        assert result.deleted_files == 2

    def test_cascade_removes_log_entries(self, template, user):
        job = _make_job(template, user, status=MailMergeJob.Status.DONE,
                        finished_offset_days=40)
        JobLogEntry.objects.create(job=job, level="info", message="x")
        JobLogEntry.objects.create(job=job, level="info", message="y")
        assert JobLogEntry.objects.count() == 2
        cleanup_expired_jobs(retention_days=30)
        assert JobLogEntry.objects.count() == 0

    def test_returns_cleanup_result(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=40)
        result = cleanup_expired_jobs(retention_days=30)
        assert isinstance(result, CleanupResult)
        assert result.dry_run is False
        assert result.candidates == 1


class TestCleanupDryRun:
    def test_dry_run_deletes_nothing(self, template, user):
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=40)
        result = cleanup_expired_jobs(retention_days=30, dry_run=True)
        assert result.dry_run is True
        assert result.candidates == 1
        assert result.deleted_jobs == 0
        assert MailMergeJob.objects.count() == 1

    def test_dry_run_counts_candidates(self, template, user):
        for _ in range(3):
            _make_job(template, user, status=MailMergeJob.Status.DONE,
                      finished_offset_days=40)
        result = cleanup_expired_jobs(retention_days=30, dry_run=True)
        assert result.candidates == 3


class TestCleanupMixed:
    def test_only_expired_terminal_jobs_are_touched(self, template, user):
        # 1× expired DONE, 1× expired FAILED → werden gelöscht
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=40)
        _make_job(template, user, status=MailMergeJob.Status.FAILED,
                  finished_offset_days=40)
        # 1× recent DONE, 1× recent FAILED → bleiben
        _make_job(template, user, status=MailMergeJob.Status.DONE,
                  finished_offset_days=10)
        _make_job(template, user, status=MailMergeJob.Status.FAILED,
                  finished_offset_days=10)
        # 1× running, 1× pending (älter als cutoff) → bleiben in jedem Fall
        _make_job(template, user, status=MailMergeJob.Status.RUNNING,
                  finished_offset_days=None, created_offset_days=999)
        _make_job(template, user, status=MailMergeJob.Status.PENDING,
                  finished_offset_days=None, created_offset_days=999)

        result = cleanup_expired_jobs(retention_days=30)
        assert result.deleted_jobs == 2
        assert MailMergeJob.objects.count() == 4