"""One-time rewrite of saved queries to parameterized metric expressions."""

import re

import click

from .extensions import db
from .models import SavedAnalysis, User
from .stats import parse_query, query_text


def rewrite(query):
    threshold = '10'
    lines = []
    for line in query.splitlines():
        match = re.fullmatch(r'\s*long run distance >= (\d+(?:\.\d+)?) km\s*', line)
        if match:
            threshold = match[1]
        else:
            lines.append(line)
    daily = any(line.strip() in {'days', 'health'} for line in lines)
    replacements = {
        'days_since_run': 'days_since_run()',
        'days_since_long_run': f'days_since_run(distance >= {threshold} km)',
        **{f'best_{km}km': f'best_time({km} km)' for km in (1, 2, 5, 10)},
        **{f'rolling_{days}d_distance': f'rolling_sum(distance, {days} days)' for days in (7, 28)},
        **{f'rolling_{days}d_count': (f'rolling_sum(sessions, {days} days)' if daily
                                    else f'rolling_count(distance, {days} days)') for days in (7, 28)},
    }
    pattern = re.compile(r'\b(' + '|'.join(replacements) + r')\b(?!\s*\()')
    result = []
    for line in lines:
        if not line.lstrip().startswith('#'):
            parts = re.split(r'("(?:[^"\\]|\\.)*")', line)
            for index in range(0, len(parts), 2):
                parts[index] = pattern.sub(lambda m: replacements[m[0]], parts[index])
            line = ''.join(parts)
        result.append(line)
    return '\n'.join(result)


def migrate(user):
    changes = []
    for row in db.session.scalars(db.select(SavedAnalysis).where(SavedAnalysis.owner_id == user.id)):
        updated = rewrite(row.query)
        if updated != row.query:
            # Validate every replacement before modifying any persisted query.
            canonical = query_text(parse_query({'query': updated}))
            parse_query({'query': canonical})
            changes.append((row, updated))
    for row, updated in changes:
        row.query = updated
    db.session.commit()
    return len(changes)


def register_cli(app):
    @app.cli.command('migrate-analysis-expressions')
    @click.option('--email', required=True)
    def migrate_queries(email):
        user = db.session.scalar(db.select(User).filter_by(email=email.strip().lower()))
        if not user:
            raise click.ClickException('Account not found.')
        try:
            count = migrate(user)
        except ValueError as error:
            db.session.rollback()
            raise click.ClickException(str(error)) from None
        click.echo(f'Updated {count} saved analyses.')