"""``retention`` sub-commands.

Ports ``scripts/Invoke-RetentionPolicy.ps1`` to Python.

* ``retention run`` — purge old artifact and log directories based on age;
  switches to aggressive retention when disk free space is low.
"""

from __future__ import annotations

import shutil
from datetime import UTC, datetime, timedelta
from pathlib import Path

import click

from ci_orchestrator.config import load_config


@click.group()
def retention() -> None:
    """Maintenance: artifact and log retention."""


@retention.command("run")
@click.option(
    "--artifact-dir",
    default=None,
    help="Artifact directory (default: CI_ARTIFACTS from config/env).",
)
@click.option(
    "--log-dir",
    default=None,
    help="Log directory (default: <CI_ROOT>/logs).",
)
@click.option(
    "--retention-days",
    default=30,
    show_default=True,
    help="Normal retention threshold in days.",
)
@click.option(
    "--aggressive-retention-days",
    default=7,
    show_default=True,
    help="Retention threshold when disk free space is below --min-free-gb.",
)
@click.option(
    "--min-free-gb",
    default=50,
    show_default=True,
    help="Switch to aggressive retention when free space drops below this value (GB).",
)
@click.option(
    "--what-if",
    is_flag=True,
    help="Dry run — log what would be deleted without actually deleting.",
)
def retention_run(
    artifact_dir: str | None,
    log_dir: str | None,
    retention_days: int,
    aggressive_retention_days: int,
    min_free_gb: int,
    what_if: bool,
) -> None:
    """Purge old artifact and log directories based on retention policy."""
    config = load_config()

    art_path = Path(artifact_dir) if artifact_dir else config.paths.artifacts
    log_path = Path(log_dir) if log_dir else config.paths.root / "logs"

    check_path = art_path if art_path.exists() else config.paths.root
    usage = shutil.disk_usage(str(check_path))
    free_gb = usage.free / (1024**3)

    aggressive = free_gb < min_free_gb
    effective_days = aggressive_retention_days if aggressive else retention_days
    cutoff = datetime.now(tz=UTC) - timedelta(days=effective_days)

    click.echo(f"[RetentionPolicy] Free space: {free_gb:.1f} GB")
    if aggressive:
        click.echo(
            f"[RetentionPolicy] WARNING: Free space below {min_free_gb} GB — "
            f"aggressive retention: {aggressive_retention_days}d",
            err=True,
        )
    else:
        click.echo(
            f"[RetentionPolicy] Normal retention: {effective_days}d "
            f"(cutoff: {cutoff.strftime('%Y-%m-%d')})"
        )

    _purge_old_dirs(art_path, "artifact", cutoff, what_if=what_if)
    _purge_old_dirs(log_path, "log", cutoff, what_if=what_if)

    usage_after = shutil.disk_usage(str(check_path))
    free_gb_after = usage_after.free / (1024**3)
    delta = free_gb_after - free_gb
    click.echo(
        f"[RetentionPolicy] Done. Free space: {free_gb_after:.1f} GB (delta: +{delta:.1f} GB)"
    )


def _purge_old_dirs(base: Path, label: str, cutoff: datetime, *, what_if: bool) -> None:
    if not base.exists():
        click.echo(f"[RetentionPolicy] {label} dir not found: {base} — skipping.")
        return

    old = [
        d
        for d in base.iterdir()
        if d.is_dir()
        and datetime.fromtimestamp(d.stat().st_mtime, tz=UTC) < cutoff
    ]

    if not old:
        click.echo(
            f"[RetentionPolicy] {label}: nothing to purge "
            f"(cutoff: {cutoff.strftime('%Y-%m-%d')})."
        )
        return

    for d in old:
        age_days = int(
            (datetime.now(tz=UTC) - datetime.fromtimestamp(d.stat().st_mtime, tz=UTC)).days
        )
        if what_if:
            click.echo(
                f"[RetentionPolicy] WhatIf: would purge {label} ({age_days}d): {d.name}"
            )
        else:
            shutil.rmtree(d, ignore_errors=True)
            click.echo(f"[RetentionPolicy] Purged {label} ({age_days}d): {d.name}")