"""Read evaluation run artifacts from disk into API-friendly structures.

A "run" is any directory under the configured output roots that contains a
metadata.json file. This service stays decoupled from rag_eval internals: it
only reads the standard artifact files (metadata.json, scores.csv, summary.md,
scenario.snapshot.yaml) that the reporting layer writes.
"""

from __future__ import annotations

import json
from pathlib import Path
from typing import Any

import pandas as pd
import yaml

from webapp.models import RunSummary


# Directory names that commonly hold run outputs, relative to the repo root.
DEFAULT_OUTPUT_ROOTS = ("outputs", "runs")


def _repo_root() -> Path:
    """Return the siemens_ragas repository root (parent of the webapp package)."""
    return Path(__file__).resolve().parents[2]


def _candidate_roots(extra_roots: list[Path] | None = None) -> list[Path]:
    """Collect existing output directories that may contain run artifacts."""
    root = _repo_root()
    roots: list[Path] = []
    for name in DEFAULT_OUTPUT_ROOTS:
        candidate = root / name
        if candidate.is_dir():
            roots.append(candidate)
    for extra in extra_roots or []:
        if extra.is_dir():
            roots.append(extra)
    return roots


def _read_json(path: Path) -> dict[str, Any]:
    """Load a JSON file, returning an empty dict on any failure."""
    try:
        return json.loads(path.read_text(encoding="utf-8"))
    except (OSError, ValueError):
        return {}


def _read_metrics_from_snapshot(run_dir: Path) -> list[str]:
    """Read the configured metric list from a scenario snapshot if present."""
    snapshot = run_dir / "scenario.snapshot.yaml"
    if not snapshot.is_file():
        return []
    try:
        payload = yaml.safe_load(snapshot.read_text(encoding="utf-8")) or {}
    except (OSError, yaml.YAMLError):
        return []
    metrics = payload.get("metrics")
    if isinstance(metrics, list):
        return [str(item) for item in metrics]
    return []


def discover_run_dirs(extra_roots: list[Path] | None = None) -> list[Path]:
    """Find every run directory (one that contains metadata.json) under the roots."""
    run_dirs: list[Path] = []
    seen: set[Path] = set()
    for root in _candidate_roots(extra_roots):
        for metadata_path in root.rglob("metadata.json"):
            run_dir = metadata_path.parent
            # A dataset-build metadata.json also exists; keep only evaluation runs
            # by requiring a scores.csv alongside, or a recognizable run metadata.
            metadata = _read_json(metadata_path)
            if "scenario_name" not in metadata:
                continue
            if run_dir in seen:
                continue
            seen.add(run_dir)
            run_dirs.append(run_dir)
    return run_dirs


def _metric_means(run_dir: Path, metrics: list[str]) -> dict[str, float | None]:
    """Compute per-metric mean scores from a run's scores.csv."""
    scores_path = run_dir / "scores.csv"
    if not scores_path.is_file():
        return {}
    try:
        frame = pd.read_csv(scores_path)
    except (OSError, ValueError, pd.errors.ParserError):
        return {}
    means: dict[str, float | None] = {}
    for metric in metrics:
        if metric in frame.columns:
            mean_value = frame[metric].mean(numeric_only=True)
            means[metric] = None if pd.isna(mean_value) else round(float(mean_value), 4)
        else:
            means[metric] = None
    return means


def build_run_summary(run_dir: Path) -> RunSummary | None:
    """Assemble a RunSummary from one run directory's artifacts."""
    metadata = _read_json(run_dir / "metadata.json")
    if "scenario_name" not in metadata:
        return None

    metrics = _read_metrics_from_snapshot(run_dir)
    if not metrics:
        # Fall back to numeric score columns inferred from the scores file.
        metrics = _infer_metrics_from_scores(run_dir)

    valid = int(metadata.get("valid_samples", 0) or 0)
    invalid = int(metadata.get("invalid_samples", 0) or 0)
    run_id = str(metadata.get("run_id") or run_dir.name)

    return RunSummary(
        run_id=run_id,
        scenario_name=str(metadata.get("scenario_name", "")),
        mode=str(metadata.get("mode", "")),
        judge_model=str(metadata.get("judge_model", "")),
        embedding_model=str(metadata.get("embedding_model", "")),
        started_at=str(metadata.get("started_at", "")),
        finished_at=str(metadata.get("finished_at", "")),
        dataset=str(metadata.get("dataset", "")),
        total_samples=valid + invalid,
        valid_samples=valid,
        invalid_samples=invalid,
        metrics=metrics,
        metric_means=_metric_means(run_dir, metrics),
        output_path=run_dir.as_posix(),
    )


# Columns in scores.csv that are sample fields rather than metric scores.
NON_METRIC_COLUMNS = {
    "sample_id",
    "question",
    "contexts",
    "answer",
    "ground_truth",
    "scenario",
    "language",
    "retrieval_config",
    "error",
    "judge_model",
    "embedding_model",
    "run_id",
    "difficulty",
    "question_type",
    "doc_id",
    "doc_name",
    "section_path",
    "page_start",
    "page_end",
    "source_chunk_ids",
    "review_status",
    "review_notes",
}


def _infer_metrics_from_scores(run_dir: Path) -> list[str]:
    """Infer metric column names from a scores.csv when no snapshot is available."""
    scores_path = run_dir / "scores.csv"
    if not scores_path.is_file():
        return []
    try:
        frame = pd.read_csv(scores_path, nrows=1)
    except (OSError, ValueError, pd.errors.ParserError):
        return []
    metrics: list[str] = []
    for column in frame.columns:
        if column in NON_METRIC_COLUMNS:
            continue
        if pd.api.types.is_numeric_dtype(frame[column]):
            metrics.append(str(column))
    return metrics


def list_run_summaries(extra_roots: list[Path] | None = None) -> list[RunSummary]:
    """Return all run summaries sorted by finish time (most recent first)."""
    summaries: list[RunSummary] = []
    for run_dir in discover_run_dirs(extra_roots):
        summary = build_run_summary(run_dir)
        if summary is not None:
            summaries.append(summary)
    summaries.sort(key=lambda item: item.finished_at or item.started_at, reverse=True)
    return summaries


def find_run_dir(run_id: str, extra_roots: list[Path] | None = None) -> Path | None:
    """Locate the run directory whose metadata or folder name matches run_id."""
    for run_dir in discover_run_dirs(extra_roots):
        metadata = _read_json(run_dir / "metadata.json")
        if str(metadata.get("run_id") or run_dir.name) == run_id:
            return run_dir
    return None


def read_scores_frame(run_dir: Path) -> pd.DataFrame:
    """Load a run's scores.csv into a dataframe, or an empty frame if missing."""
    scores_path = run_dir / "scores.csv"
    if not scores_path.is_file():
        return pd.DataFrame()
    try:
        return pd.read_csv(scores_path)
    except (OSError, ValueError, pd.errors.ParserError):
        return pd.DataFrame()


def read_summary_markdown(run_dir: Path) -> str:
    """Return the human-readable summary.md for a run, or an empty string."""
    summary_path = run_dir / "summary.md"
    if not summary_path.is_file():
        return ""
    try:
        return summary_path.read_text(encoding="utf-8")
    except OSError:
        return ""


def read_advice_markdown(run_dir: Path) -> str:
    """Return the optimization_advice.md for a run, or an empty string if not generated."""
    advice_path = run_dir / "optimization_advice.md"
    if not advice_path.is_file():
        return ""
    try:
        return advice_path.read_text(encoding="utf-8")
    except OSError:
        return ""