"""
Data Analysis Script using DuckDB.

Analyzes Excel (.xlsx/.xls) and CSV files using DuckDB's in-process SQL engine.
Supports schema inspection, SQL queries, statistical summaries, and result export.
"""

import argparse
import hashlib
import json
import logging
import os
import re
import sys
import tempfile
from collections import Counter

logging.basicConfig(level=logging.INFO, format="%(message)s")
logger = logging.getLogger(__name__)

try:
    import duckdb
except ImportError:
    raise SystemExit(
        "Missing duckdb. Prepare this Python environment with: python -m pip install duckdb openpyxl"
    ) from None

try:
    import openpyxl  # noqa: F401
except ImportError:
    raise SystemExit(
        "Missing openpyxl. Prepare this Python environment with: python -m pip install duckdb openpyxl"
    ) from None

# Cache directory for persistent DuckDB databases
CACHE_DIR = os.path.join(tempfile.gettempdir(), ".data-analysis-cache")
TABLE_MAP_SUFFIX = ".table_map.json"


def compute_files_hash(files: list[str]) -> str:
    """Hash the ordered names and contents that determine the loaded table map."""
    # A new namespace also prevents reuse of maps built by the old allocator.
    hasher = hashlib.sha256(b"data-analysis-inputs-v2\0")
    for file_path in files:
        name = os.fsencode(os.path.basename(file_path))
        hasher.update(len(name).to_bytes(8, "big"))
        hasher.update(name)
        file_hasher = hashlib.sha256()
        try:
            with open(file_path, "rb") as f:
                while chunk := f.read(8192):
                    file_hasher.update(chunk)
        except OSError:
            # Keep unreadable paths distinct, including POSIX surrogate escapes.
            hasher.update(b"missing\0")
            file_hasher = hashlib.sha256(os.fsencode(file_path))
        else:
            hasher.update(b"readable\0")
        # Fixed-width digests preserve file boundaries, even for empty files.
        hasher.update(file_hasher.digest())
    return hasher.hexdigest()


def get_cache_db_path(files_hash: str) -> str:
    """Get the path to the cached DuckDB database file."""
    os.makedirs(CACHE_DIR, exist_ok=True)
    return os.path.join(CACHE_DIR, f"{files_hash}.duckdb")


def get_table_map_path(files_hash: str) -> str:
    """Get the path to the cached table map JSON file."""
    return os.path.join(CACHE_DIR, f"{files_hash}{TABLE_MAP_SUFFIX}")


def save_table_map(files_hash: str, table_map: dict[str, str]) -> None:
    """Save table map to a JSON file alongside the cached DB."""
    path = get_table_map_path(files_hash)
    with open(path, "w", encoding="utf-8") as f:
        json.dump(table_map, f, ensure_ascii=False)


def load_table_map(files_hash: str) -> dict[str, str] | None:
    """Load table map from cache. Returns None if not found."""
    path = get_table_map_path(files_hash)
    if not os.path.exists(path):
        return None
    try:
        with open(path, "r", encoding="utf-8") as f:
            return json.load(f)
    except Exception:
        return None


def sanitize_table_name(name: str) -> str:
    """Sanitize a sheet/file name into a valid SQL table name."""
    sanitized = re.sub(r"[^\w]", "_", name)
    if sanitized and sanitized[0].isdigit():
        sanitized = f"t_{sanitized}"
    return sanitized


def _quote_identifier(name: str) -> str:
    """Quote a SQL identifier, including embedded double quotes."""
    return '"' + name.replace('"', '""') + '"'


def _allocate_table_names(name: str, table_map: dict[str, str]) -> tuple[str, str]:
    """Keep lookup aliases and SQL names unique, including case-only collisions."""
    reserved = {n.casefold() for n in (*table_map.keys(), *table_map.values())}
    base = sanitize_table_name(name)
    table_name = base
    counter = 1
    while table_name.casefold() in reserved:
        table_name = f"{base}_{counter}"
        counter += 1
    # An original name must never redirect an earlier canonical SQL name.
    alias = table_name if name.casefold() in reserved else name
    return alias, table_name


def load_files(con: duckdb.DuckDBPyConnection, files: list[str]) -> dict[str, str]:
    """
    Load Excel/CSV files into DuckDB tables.

    Returns unique lookup aliases mapped to their canonical SQL table names.
    """
    con.execute("INSTALL spatial; LOAD spatial;")
    table_map: dict[str, str] = {}

    for file_path in files:
        if not os.path.exists(file_path):
            logger.error(f"File not found: {file_path}")
            continue

        ext = os.path.splitext(file_path)[1].lower()

        if ext in (".xlsx", ".xls"):
            _load_excel(con, file_path, table_map)
        elif ext == ".csv":
            _load_csv(con, file_path, table_map)
        else:
            logger.warning(f"Unsupported file format: {ext} ({file_path})")

    return table_map


def _load_excel(
    con: duckdb.DuckDBPyConnection, file_path: str, table_map: dict[str, str]
) -> None:
    """Load all sheets from an Excel file into DuckDB tables."""
    import openpyxl

    wb = openpyxl.load_workbook(file_path, read_only=True, data_only=True)
    sheet_names = wb.sheetnames
    wb.close()

    for sheet_name in sheet_names:
        alias, table_name = _allocate_table_names(sheet_name, table_map)

        try:
            con.execute(
                f"""
                CREATE TABLE {_quote_identifier(table_name)} AS
                SELECT * FROM st_read(
                    ?,
                    layer = ?,
                    open_options = ['HEADERS=FORCE', 'FIELD_TYPES=AUTO']
                )
            """,
                [file_path, sheet_name],
            )
            table_map[alias] = table_name
            row_count = con.execute(
                f"SELECT COUNT(*) FROM {_quote_identifier(table_name)}"
            ).fetchone()[0]
            logger.info(
                f"  Loaded sheet '{sheet_name}' -> table '{table_name}' ({row_count} rows)"
            )
        except Exception as e:
            logger.warning(f"  Failed to load sheet '{sheet_name}': {e}")


def _load_csv(
    con: duckdb.DuckDBPyConnection, file_path: str, table_map: dict[str, str]
) -> None:
    """Load a CSV file into a DuckDB table."""
    base_name = os.path.splitext(os.path.basename(file_path))[0]
    alias, table_name = _allocate_table_names(base_name, table_map)

    try:
        con.execute(
            f"""
            CREATE TABLE {_quote_identifier(table_name)} AS
            SELECT * FROM read_csv_auto(?)
        """,
            [file_path],
        )
        table_map[alias] = table_name
        row_count = con.execute(
            f"SELECT COUNT(*) FROM {_quote_identifier(table_name)}"
        ).fetchone()[0]
        logger.info(
            f"  Loaded CSV '{base_name}' -> table '{table_name}' ({row_count} rows)"
        )
    except Exception as e:
        logger.warning(f"  Failed to load CSV '{base_name}': {e}")


def action_inspect(con: duckdb.DuckDBPyConnection, table_map: dict[str, str]) -> str:
    """Inspect the schema of all loaded tables."""
    output_parts = []

    for original_name, table_name in table_map.items():
        output_parts.append(f"\n{'=' * 60}")
        output_parts.append(f'Table: {original_name} (SQL name: "{table_name}")')
        output_parts.append(f"{'=' * 60}")

        # Get row count
        row_count = con.execute(
            f"SELECT COUNT(*) FROM {_quote_identifier(table_name)}"
        ).fetchone()[0]
        output_parts.append(f"Rows: {row_count}")

        # Get column info
        columns = con.execute(f"DESCRIBE {_quote_identifier(table_name)}").fetchall()
        output_parts.append(f"\nColumns ({len(columns)}):")
        output_parts.append(f"{'Name':<30} {'Type':<15} {'Nullable'}")
        output_parts.append(f"{'-' * 30} {'-' * 15} {'-' * 8}")
        for col in columns:
            col_name, col_type, nullable = col[0], col[1], col[2]
            output_parts.append(f"{col_name:<30} {col_type:<15} {nullable}")

        # Get non-null counts per column
        col_names = [col[0] for col in columns]
        non_null_parts = []
        for c in col_names:
            non_null_parts.append(f"COUNT({_quote_identifier(c)})")
        non_null_sql = (
            f"SELECT {', '.join(non_null_parts)} FROM {_quote_identifier(table_name)}"
        )
        try:
            non_null_counts = con.execute(non_null_sql).fetchone()
            output_parts.append("\nNon-null counts:")
            for i, c in enumerate(col_names):
                output_parts.append(f"  {c}: {non_null_counts[i]} / {row_count}")
        except Exception:
            pass

        # Sample data (first 5 rows)
        output_parts.append("\nSample data (first 5 rows):")
        try:
            sample = con.execute(
                f"SELECT * FROM {_quote_identifier(table_name)} LIMIT 5"
            ).fetchdf()
            output_parts.append(sample.to_string(index=False))
        except Exception:
            sample = con.execute(
                f"SELECT * FROM {_quote_identifier(table_name)} LIMIT 5"
            ).fetchall()
            header = [col[0] for col in columns]
            output_parts.append("  " + " | ".join(header))
            for row in sample:
                output_parts.append("  " + " | ".join(str(v) for v in row))

    result = "\n".join(output_parts)
    print(result)
    return result


def action_query(
    con: duckdb.DuckDBPyConnection,
    sql: str,
    table_map: dict[str, str],
    output_file: str | None = None,
) -> str:
    """Execute a SQL query and return/export results."""
    try:
        # Let DuckDB resolve identifiers without rewriting SQL literals, column
        # names, comments, or CTEs. Temporary views also work on read-only caches.
        for original_name, table_name in table_map.items():
            if original_name != table_name:
                con.execute(
                    f"CREATE OR REPLACE TEMP VIEW {_quote_identifier(original_name)} "
                    f"AS SELECT * FROM main.{_quote_identifier(table_name)}"
                )
        result = con.execute(sql)
        columns = [desc[0] for desc in result.description]
        rows = result.fetchall()
    except Exception as e:
        error_msg = f"SQL Error: {e}\n\nAvailable tables:\n"
        for orig, tbl in table_map.items():
            cols = con.execute(f"DESCRIBE {_quote_identifier(tbl)}").fetchall()
            col_names = [c[0] for c in cols]
            error_msg += f'  "{tbl}" ({orig}): {", ".join(col_names)}\n'
        print(error_msg)
        return error_msg

    # Format output
    if output_file:
        return _export_results(columns, rows, output_file)

    # Print as table
    return _format_table(columns, rows)


def _format_table(columns: list[str], rows: list[tuple]) -> str:
    """Format query results as a readable table."""
    if not rows:
        msg = "Query returned 0 rows."
        print(msg)
        return msg

    # Calculate column widths
    col_widths = [len(str(c)) for c in columns]
    for row in rows:
        for i, val in enumerate(row):
            col_widths[i] = max(col_widths[i], len(str(val)))

    # Cap column width
    max_width = 40
    col_widths = [min(w, max_width) for w in col_widths]

    # Build table
    parts = []
    header = " | ".join(str(c).ljust(col_widths[i]) for i, c in enumerate(columns))
    separator = "-+-".join("-" * col_widths[i] for i in range(len(columns)))
    parts.append(header)
    parts.append(separator)
    for row in rows:
        row_str = " | ".join(
            str(v)[:max_width].ljust(col_widths[i]) for i, v in enumerate(row)
        )
        parts.append(row_str)

    parts.append(f"\n({len(rows)} rows)")
    result = "\n".join(parts)
    print(result)
    return result


def _markdown_cell(value: object) -> str:
    """Keep table delimiters and line breaks inside a single Markdown cell."""
    return (
        str(value)
        .replace("\\", "\\\\")
        .replace("|", "\\|")
        .replace("\r\n", "\n")
        .replace("\r", "\n")
        .replace("\n", "<br>")
    )


def _export_results(columns: list[str], rows: list[tuple], output_file: str) -> str:
    """Export query results to a file (CSV, JSON, or Markdown)."""
    os.makedirs(os.path.dirname(output_file), exist_ok=True)
    ext = os.path.splitext(output_file)[1].lower()

    if ext == ".csv":
        import csv

        with open(output_file, "w", newline="", encoding="utf-8") as f:
            writer = csv.writer(f)
            writer.writerow(columns)
            writer.writerows(rows)

    elif ext == ".json":
        duplicates = [name for name, count in Counter(columns).items() if count > 1]
        if duplicates:
            raise ValueError(
                "JSON export requires unique column names; duplicates: "
                + ", ".join(repr(name) for name in duplicates)
                + ". Use SQL aliases (AS) to give each result column a distinct name."
            )
        records = []
        for row in rows:
            record = {}
            for i, col in enumerate(columns):
                val = row[i]
                # Handle non-JSON-serializable types
                if hasattr(val, "isoformat"):
                    val = val.isoformat()
                elif isinstance(val, (bytes, bytearray)):
                    val = val.hex()
                record[col] = val
            records.append(record)
        with open(output_file, "w", encoding="utf-8") as f:
            json.dump(records, f, indent=2, ensure_ascii=False, default=str)

    elif ext == ".md":
        with open(output_file, "w", encoding="utf-8") as f:
            # Header
            f.write("| " + " | ".join(_markdown_cell(c) for c in columns) + " |\n")
            f.write("| " + " | ".join("---" for _ in columns) + " |\n")
            # Rows
            for row in rows:
                f.write("| " + " | ".join(_markdown_cell(v) for v in row) + " |\n")
    else:
        msg = f"Unsupported output format: {ext}. Use .csv, .json, or .md"
        print(msg)
        return msg

    msg = f"Results exported to {output_file} ({len(rows)} rows)"
    print(msg)
    return msg


def action_summary(
    con: duckdb.DuckDBPyConnection,
    table_name: str,
    table_map: dict[str, str],
) -> str:
    """Generate statistical summary for a table."""
    # Resolve table name
    resolved = _quote_identifier(table_map.get(table_name, table_name))

    try:
        columns = con.execute(f"DESCRIBE {resolved}").fetchall()
    except Exception:
        available = ", ".join(f'"{t}" ({o})' for o, t in table_map.items())
        msg = f"Table '{table_name}' not found. Available tables: {available}"
        print(msg)
        return msg

    row_count = con.execute(f"SELECT COUNT(*) FROM {resolved}").fetchone()[0]

    output_parts = []
    output_parts.append(f"\nStatistical Summary: {table_name}")
    output_parts.append(f"Total rows: {row_count}")
    output_parts.append(f"{'=' * 70}")

    numeric_types = {
        "BIGINT",
        "INTEGER",
        "SMALLINT",
        "TINYINT",
        "DOUBLE",
        "FLOAT",
        "DECIMAL",
        "HUGEINT",
        "REAL",
        "NUMERIC",
    }

    for col in columns:
        col_name, col_type = col[0], col[1].upper()
        quoted_col = _quote_identifier(col_name)
        output_parts.append(f"\n--- {col_name} ({col[1]}) ---")

        # Check base type (strip parameterized parts)
        base_type = re.sub(r"\(.*\)", "", col_type).strip()

        if base_type in numeric_types:
            try:
                stats = con.execute(f"""
                    SELECT
                        COUNT({quoted_col}) as count,
                        AVG({quoted_col})::DOUBLE as mean,
                        STDDEV({quoted_col})::DOUBLE as std,
                        MIN({quoted_col}) as min,
                        QUANTILE_CONT({quoted_col}, 0.25) as q25,
                        MEDIAN({quoted_col}) as median,
                        QUANTILE_CONT({quoted_col}, 0.75) as q75,
                        MAX({quoted_col}) as max,
                        COUNT(*) - COUNT({quoted_col}) as null_count
                    FROM {resolved}
                """).fetchone()
                labels = [
                    "count",
                    "mean",
                    "std",
                    "min",
                    "25%",
                    "50%",
                    "75%",
                    "max",
                    "nulls",
                ]
                for label, val in zip(labels, stats):
                    if isinstance(val, float):
                        output_parts.append(f"  {label:<8}: {val:,.4f}")
                    else:
                        output_parts.append(f"  {label:<8}: {val}")
            except Exception as e:
                output_parts.append(f"  Error computing stats: {e}")
        else:
            try:
                stats = con.execute(f"""
                    SELECT
                        COUNT({quoted_col}) as count,
                        COUNT(DISTINCT {quoted_col}) as unique_count,
                        MODE({quoted_col}) as mode_val,
                        COUNT(*) - COUNT({quoted_col}) as null_count
                    FROM {resolved}
                """).fetchone()
                output_parts.append(f"  count   : {stats[0]}")
                output_parts.append(f"  unique  : {stats[1]}")
                output_parts.append(f"  top     : {stats[2]}")
                output_parts.append(f"  nulls   : {stats[3]}")

                # Show top 5 values
                top_vals = con.execute(f"""
                    SELECT {quoted_col}, COUNT(*) as freq
                    FROM {resolved}
                    WHERE {quoted_col} IS NOT NULL
                    GROUP BY {quoted_col}
                    ORDER BY freq DESC
                    LIMIT 5
                """).fetchall()
                if top_vals:
                    output_parts.append("  top values:")
                    for val, freq in top_vals:
                        pct = (freq / row_count * 100) if row_count > 0 else 0
                        output_parts.append(f"    {val}: {freq} ({pct:.1f}%)")
            except Exception as e:
                output_parts.append(f"  Error computing stats: {e}")

    result = "\n".join(output_parts)
    print(result)
    return result


def main():
    parser = argparse.ArgumentParser(description="Analyze Excel/CSV files using DuckDB")
    parser.add_argument(
        "--files",
        nargs="+",
        required=True,
        help="Paths to Excel (.xlsx/.xls) or CSV files",
    )
    parser.add_argument(
        "--action",
        required=True,
        choices=["inspect", "query", "summary"],
        help="Action to perform: inspect, query, or summary",
    )
    parser.add_argument(
        "--sql",
        type=str,
        default=None,
        help="SQL query to execute (required for 'query' action)",
    )
    parser.add_argument(
        "--table",
        type=str,
        default=None,
        help="Table name for summary (required for 'summary' action)",
    )
    parser.add_argument(
        "--output-file",
        type=str,
        default=None,
        help="Path to export results (CSV/JSON/MD)",
    )
    args = parser.parse_args()

    # Validate arguments
    if args.action == "query" and not args.sql:
        parser.error("--sql is required for 'query' action")
    if args.action == "summary" and not args.table:
        parser.error("--table is required for 'summary' action")

    # Compute file hash for caching
    files_hash = compute_files_hash(args.files)
    db_path = get_cache_db_path(files_hash)
    cached_table_map = load_table_map(files_hash)

    if cached_table_map and os.path.exists(db_path):
        # Cache hit: connect to existing DB
        logger.info(f"Cache hit! Using cached database: {db_path}")
        con = duckdb.connect(db_path, read_only=True)
        table_map = cached_table_map
        logger.info(
            f"Loaded {len(table_map)} table(s) from cache: {', '.join(table_map.keys())}"
        )
    else:
        # Cache miss: load files and persist to DB
        logger.info("Loading files (first time, will cache for future use)...")
        con = duckdb.connect(db_path)
        table_map = load_files(con, args.files)

        if not table_map:
            logger.error("No tables were loaded. Check file paths and formats.")
            # Clean up empty DB file
            con.close()
            if os.path.exists(db_path):
                os.remove(db_path)
            sys.exit(1)

        # Save table map for future cache lookups
        save_table_map(files_hash, table_map)
        logger.info(
            f"\nLoaded {len(table_map)} table(s): {', '.join(table_map.keys())}"
        )
        logger.info(f"Cached database saved to: {db_path}")

    try:
        if args.action == "inspect":
            action_inspect(con, table_map)
        elif args.action == "query":
            action_query(con, args.sql, table_map, args.output_file)
        elif args.action == "summary":
            action_summary(con, args.table, table_map)
    except ValueError as exc:
        sys.exit(f"Error: {exc}")
    finally:
        con.close()


if __name__ == "__main__":
    main()