#!/usr/bin/env python3
"""Compare local regenerated model inputs with committed inputs.

This script is intentionally read-only with respect to data/. It writes a report
under _local/reports/ and exits nonzero when files differ or are missing.
"""

from __future__ import annotations

import csv
import hashlib
import os
from pathlib import Path
from typing import Iterable


MODEL_INPUTS = [
    "text_data.csv",
    "expert.csv",
    "lr_data.csv",
    "union_mapping.csv",
    "party_families.csv",
]


def normalized_rows(path: Path) -> Iterable[list[str]]:
    with path.open(newline="", encoding="utf-8") as fh:
        reader = csv.reader(fh)
        for row in reader:
            yield ["" if value is None else value.strip() for value in row]


def normalized_hash(path: Path) -> str:
    h = hashlib.sha256()
    for row in normalized_rows(path):
        h.update(("\x1f".join(row) + "\n").encode("utf-8"))
    return h.hexdigest()


def csv_shape(path: Path) -> tuple[int, int, list[str]]:
    with path.open(newline="", encoding="utf-8") as fh:
        reader = csv.reader(fh)
        try:
            header = next(reader)
        except StopIteration:
            return 0, 0, []
        rows = sum(1 for _ in reader)
        return rows, len(header), header


def first_difference(left: Path, right: Path, max_scan: int = 100000) -> str:
    for idx, (lrow, rrow) in enumerate(zip(normalized_rows(left), normalized_rows(right)), start=1):
        if lrow != rrow:
            return f"line {idx}: committed={lrow[:8]!r} generated={rrow[:8]!r}"
        if idx >= max_scan:
            break
    return "no differing row found in scan window; row counts may differ"


def main() -> int:
    repo_root = Path(__file__).resolve().parents[1]
    committed_dir = Path(os.environ.get("PARTY2D_COMMITTED_INPUT_DIR", repo_root / "data"))
    generated_dir = Path(os.environ.get("PARTY2D_GENERATED_INPUT_DIR", repo_root / "_local" / "generated-inputs"))
    report_dir = Path(os.environ.get("PARTY2D_REPORT_DIR", repo_root / "_local" / "reports"))
    report_dir.mkdir(parents=True, exist_ok=True)
    report_path = report_dir / "input_comparison.md"

    lines: list[str] = []
    lines.append("# Generated input comparison")
    lines.append("")
    lines.append(f"Committed input dir: `{committed_dir}`")
    lines.append(f"Generated input dir: `{generated_dir}`")
    lines.append("")
    lines.append("| file | status | committed rows | generated rows | committed hash | generated hash | notes |")
    lines.append("| --- | --- | ---: | ---: | --- | --- | --- |")

    ok = True
    for name in MODEL_INPUTS:
        committed = committed_dir / name
        generated = generated_dir / name
        if not committed.exists() or not generated.exists():
            ok = False
            lines.append(
                f"| `{name}` | missing |  |  |  |  | committed exists={committed.exists()}, generated exists={generated.exists()} |"
            )
            continue

        c_rows, c_cols, c_header = csv_shape(committed)
        g_rows, g_cols, g_header = csv_shape(generated)
        c_hash = normalized_hash(committed)
        g_hash = normalized_hash(generated)
        same = c_hash == g_hash
        status = "match" if same else "diff"
        if not same:
            ok = False
        notes = []
        if c_cols != g_cols:
            notes.append(f"columns {c_cols}!={g_cols}")
        if c_header != g_header:
            notes.append("header differs")
        if c_rows != g_rows:
            notes.append(f"rows {c_rows}!={g_rows}")
        if not same and not notes:
            notes.append(first_difference(committed, generated))
        lines.append(
            f"| `{name}` | {status} | {c_rows} | {g_rows} | `{c_hash[:12]}` | `{g_hash[:12]}` | {'; '.join(notes)} |"
        )

    lines.append("")
    lines.append("Committed inputs were not modified by this comparison.")
    report_path.write_text("\n".join(lines) + "\n", encoding="utf-8")
    print(f"Wrote comparison report: {report_path}")
    if ok:
        print("Generated inputs match committed inputs.")
        return 0
    print("Generated inputs differ from committed inputs or are missing.")
    return 1


if __name__ == "__main__":
    raise SystemExit(main())