# Generated for QI multi-department support.
#
# Order matters:
#   1. Add the new `departments` M2M (blank).
#   2. Copy each existing `department_id` into the M2M, then rebuild the derived
#      `team_members` set from each department's champion + manager (and the
#      project lead). The sync logic is inlined here (not imported from the
#      model) so the migration stays stable as the model method evolves.
#   3. Remove the old single `department` FK.

from django.db import migrations, models


def copy_department_and_sync_team(apps, schema_editor):
    QIProject = apps.get_model("projects", "QIProject")
    Staff = apps.get_model("organizations", "Staff")

    missing_manager_profile = 0
    for project in QIProject.objects.exclude(department__isnull=True):
        old_dept = project.department
        # M2M add via the through manager (project has just been saved with the new field).
        if old_dept and old_dept not in project.departments.all():
            project.departments.add(old_dept)

        # Rebuild derived team_members: champion (Staff) + manager.staff_profile (Staff),
        # plus the project lead. De-duped; nulls skipped.
        pks = set()
        for dept in project.departments.all():
            champion_id = getattr(dept, "champion_id", None)
            if champion_id:
                pks.add(champion_id)
            manager_user_id = getattr(dept, "manager_id", None)
            if manager_user_id:
                manager_user = dept.manager
                if manager_user is not None and hasattr(manager_user, "staff_profile"):
                    sp = manager_user.staff_profile
                    if sp is not None and sp.id:
                        pks.add(sp.id)
                    else:
                        missing_manager_profile += 1
        if project.project_lead_id:
            pks.add(project.project_lead_id)

        if pks:
            project.team_members.set(Staff.objects.filter(pk__in=pks))

    if missing_manager_profile:
        # Surface how many manager links could not be added (no staff_profile).
        print(f"    [qi_multi_department] {missing_manager_profile} department manager(s) "
              f"had no staff_profile and were excluded from the derived team.")


def remove_team_backreference(apps, schema_editor):
    # Reverse is a no-op: we cannot reconstruct the single FK from the M2M losslessly.
    pass


class Migration(migrations.Migration):

    dependencies = [
        ("organizations", "0015_hospital_branding"),
        ("projects", "0003_alter_qiproject_project_lead_and_more"),
    ]

    operations = [
        migrations.AddField(
            model_name="qiproject",
            name="departments",
            field=models.ManyToManyField(
                blank=True,
                help_text="Departments involved in this QI project. Team membership is derived from each department's champion and manager.",
                related_name="qi_projects",
                to="organizations.department",
            ),
        ),
        migrations.RunPython(copy_department_and_sync_team, remove_team_backreference),
        migrations.RemoveField(
            model_name="qiproject",
            name="department",
        ),
    ]