"""
Management command to normalize muscle names in the database.

Fixes casing duplicates (e.g. "Quads" vs "quads") and updates
ExerciseMuscle records to point to the canonical muscle entries.

Usage:
    python manage.py normalize_muscles           # apply changes
    python manage.py normalize_muscles --dry-run  # preview only
"""

from django.core.management.base import BaseCommand

from muscle.models import Muscle, ExerciseMuscle
from generator.services.muscle_normalizer import normalize_muscle_name


class Command(BaseCommand):
    help = 'Normalize muscle names (fix casing duplicates) and consolidate ExerciseMuscle records.'

    def add_arguments(self, parser):
        parser.add_argument(
            '--dry-run',
            action='store_true',
            help='Preview changes without modifying the database.',
        )

    def handle(self, *args, **options):
        dry_run = options['dry_run']
        if dry_run:
            self.stdout.write(self.style.WARNING('DRY RUN - no changes will be made.\n'))

        muscles = Muscle.objects.all().order_by('name')
        self.stdout.write(f'Total muscles in DB: {muscles.count()}\n')

        # Build a mapping: canonical_name -> list of Muscle objects with that canonical name
        canonical_map = {}
        for m in muscles:
            canonical = normalize_muscle_name(m.name)
            if canonical is None:
                canonical = m.name.strip().lower()
            canonical_map.setdefault(canonical, []).append(m)

        # Identify duplicates (canonical names with > 1 Muscle record)
        duplicates = {k: v for k, v in canonical_map.items() if len(v) > 1}

        if not duplicates:
            self.stdout.write(self.style.SUCCESS('No duplicate muscles found. Nothing to normalize.'))
            return

        self.stdout.write(f'Found {len(duplicates)} canonical names with duplicates:\n')

        merged_count = 0
        reassigned_count = 0

        for canonical, muscle_list in sorted(duplicates.items()):
            names = [m.name for m in muscle_list]
            self.stdout.write(f'\n  "{canonical}" <- {names}')

            # Keep the first one (or the one whose name already matches canonical)
            keep = None
            for m in muscle_list:
                if m.name == canonical:
                    keep = m
                    break
            if keep is None:
                keep = muscle_list[0]

            to_merge = [m for m in muscle_list if m.pk != keep.pk]

            for old_muscle in to_merge:
                # Reassign ExerciseMuscle records from old_muscle to keep
                em_records = ExerciseMuscle.objects.filter(muscle=old_muscle)
                count = em_records.count()

                if count > 0:
                    self.stdout.write(f'    Reassigning {count} ExerciseMuscle records: '
                                      f'"{old_muscle.name}" (id={old_muscle.pk}) -> '
                                      f'"{keep.name}" (id={keep.pk})')
                    if not dry_run:
                        # Check for conflicts (same exercise already linked to keep)
                        for em in em_records:
                            existing = ExerciseMuscle.objects.filter(
                                exercise=em.exercise, muscle=keep
                            ).exists()
                            if existing:
                                em.delete()
                            else:
                                em.muscle = keep
                                em.save()
                        reassigned_count += count

                # Rename keep to canonical if needed
                if keep.name != canonical and not dry_run:
                    keep.name = canonical
                    keep.save()

                # Delete the duplicate
                self.stdout.write(f'    Deleting duplicate: "{old_muscle.name}" (id={old_muscle.pk})')
                if not dry_run:
                    old_muscle.delete()
                    merged_count += 1

        # Also fix names that aren't duplicates but have wrong casing
        rename_count = 0
        for canonical, muscle_list in canonical_map.items():
            if len(muscle_list) == 1:
                m = muscle_list[0]
                if m.name != canonical:
                    self.stdout.write(f'\n  Renaming: "{m.name}" -> "{canonical}"')
                    if not dry_run:
                        m.name = canonical
                        m.save()
                    rename_count += 1

        self.stdout.write('\n')
        if dry_run:
            self.stdout.write(self.style.WARNING(
                f'DRY RUN complete. Would merge {merged_count} duplicates, '
                f'reassign {reassigned_count} ExerciseMuscle records, '
                f'rename {rename_count} muscles.'
            ))
        else:
            remaining = Muscle.objects.count()
            self.stdout.write(self.style.SUCCESS(
                f'Done. Merged {merged_count} duplicates, '
                f'reassigned {reassigned_count} ExerciseMuscle records, '
                f'renamed {rename_count} muscles. '
                f'{remaining} muscles remaining.'
            ))