"""
Metrics history and viability tracking.

Converts check results into timestamped snapshots and maintains a
persistent history file for trend analysis.
"""

from __future__ import annotations

import uuid
from datetime import datetime, timezone
from pathlib import Path
from typing import Any, Dict, List, Optional

import yaml

from markitect.infospace.checks.orchestrator import CheckReport
from markitect.infospace.config import InfospaceConfig
from markitect.infospace.evaluation import EvaluationSnapshot, MetricValue
from markitect.infospace.evaluation_io import (
    append_to_history,
    diff_snapshots,
    read_history,
)
from markitect.infospace.state import ViabilityResult


# ── Snapshot creation ────────────────────────────────────────────────


def _concern_for_metric(name: str) -> str:
    """Map a metric name to its concern label."""
    mapping = {
        "redundancy_ratio": "C1",
        "coverage_ratio": "C2",
        "coherence_components": "C3",
        "modularity": "C3",
        "consistency_cycles": "C4",
        "granularity_entropy": "C5",
    }
    return mapping.get(name, "")


def snapshot_from_checks(
    check_report: CheckReport,
    entity_count: int,
    schema_name: str = "default",
    metadata: Optional[Dict[str, Any]] = None,
) -> EvaluationSnapshot:
    """Create an :class:`EvaluationSnapshot` from collection check results.

    Args:
        check_report: Output from :func:`run_all_checks`.
        entity_count: Number of entities checked.
        schema_name: Schema identifier for the snapshot.
        metadata: Optional extra metadata to attach.

    Returns:
        A snapshot containing the check metrics as collection_metrics.
    """
    metrics_dict = check_report.metrics()
    collection_metrics = [
        MetricValue(
            name=name,
            value=value,
            concern=_concern_for_metric(name),
        )
        for name, value in sorted(metrics_dict.items())
    ]

    return EvaluationSnapshot(
        snapshot_id=str(uuid.uuid4())[:8],
        created_at=datetime.now(timezone.utc),
        schema_name=schema_name,
        entity_count=entity_count,
        collection_metrics=collection_metrics,
        metadata=metadata or {},
    )


# ── Metrics file I/O ────────────────────────────────────────────────


def write_metrics_file(metrics: Dict[str, float], path: Path) -> None:
    """Write the latest metrics to a simple YAML file.

    This file is used by ``markitect infospace viability`` for quick
    threshold checking.
    """
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(
        yaml.safe_dump(
            {k: round(v, 6) for k, v in sorted(metrics.items())},
            default_flow_style=False,
            sort_keys=True,
        ),
        encoding="utf-8",
    )


def read_metrics_file(path: Path) -> Dict[str, float]:
    """Read the latest metrics from a YAML file."""
    if not path.is_file():
        return {}
    raw = yaml.safe_load(path.read_text(encoding="utf-8"))
    if not isinstance(raw, dict):
        return {}
    return {k: float(v) for k, v in raw.items() if isinstance(v, (int, float))}


# ── History operations ───────────────────────────────────────────────


def record_check_results(
    check_report: CheckReport,
    config: InfospaceConfig,
    root: Path,
    entity_count: int,
) -> EvaluationSnapshot:
    """Record check results: save metrics file and append to history.

    Args:
        check_report: Output from ``run_all_checks()``.
        config: The infospace configuration.
        root: Project root directory.
        entity_count: Number of entities checked.

    Returns:
        The snapshot that was recorded.
    """
    metrics_dir = root / config.metrics_dir
    metrics = check_report.metrics()

    # Save latest metrics
    write_metrics_file(metrics, metrics_dir / "metrics.yaml")

    # Create and append snapshot
    snapshot = snapshot_from_checks(
        check_report,
        entity_count=entity_count,
        metadata={"source": "collection-checks"},
    )
    append_to_history(snapshot, metrics_dir / "history.yaml")

    return snapshot


def get_history(config: InfospaceConfig, root: Path) -> List[EvaluationSnapshot]:
    """Read the full metrics history for an infospace."""
    history_path = root / config.metrics_dir / "history.yaml"
    if not history_path.is_file():
        return []
    return read_history(history_path)


def get_latest_snapshot(
    config: InfospaceConfig, root: Path
) -> Optional[EvaluationSnapshot]:
    """Get the most recent snapshot from the history."""
    history = get_history(config, root)
    return history[-1] if history else None


def find_snapshot_by_date(
    history: List[EvaluationSnapshot], date_str: str
) -> Optional[EvaluationSnapshot]:
    """Find the snapshot closest to a given date string.

    Args:
        history: List of snapshots in chronological order.
        date_str: Date string in ``YYYY-MM-DD`` or ``YYYY-MM-DDTHH:MM:SS`` format.

    Returns:
        The snapshot closest to the given date, or ``None`` if history is empty.
    """
    if not history:
        return None

    # Parse the target date
    try:
        if "T" in date_str:
            target = datetime.fromisoformat(date_str)
        else:
            target = datetime.fromisoformat(date_str + "T00:00:00")
    except ValueError:
        return None

    # Make timezone-aware if needed
    if target.tzinfo is None:
        target = target.replace(tzinfo=timezone.utc)

    best = None
    best_delta = None
    for snap in history:
        snap_dt = snap.created_at
        if snap_dt.tzinfo is None:
            snap_dt = snap_dt.replace(tzinfo=timezone.utc)
        delta = abs((snap_dt - target).total_seconds())
        if best_delta is None or delta < best_delta:
            best = snap
            best_delta = delta

    return best


def metric_trend(
    history: List[EvaluationSnapshot], metric_name: str
) -> List[Dict[str, Any]]:
    """Extract a single metric's values across the history.

    Returns a list of ``{"date": iso_str, "value": float}`` entries
    for each snapshot that contains the metric.
    """
    trend: List[Dict[str, Any]] = []
    for snap in history:
        for m in snap.collection_metrics:
            if m.name == metric_name:
                trend.append({
                    "date": snap.created_at.isoformat(),
                    "value": m.value,
                })
                break
    return trend