#!/usr/bin/env python3
"""Csvview — CSV/TSV viewer with column alignment, filtering, and search."""
import argparse, csv, io, os, sys, math


def color(text, code):
    return f"\033[{code}m{text}\033[0m" if sys.stdout.isatty() else text


def read_csv(path, delimiter=","):
    if path == "-":
        content = sys.stdin.read()
        reader = csv.reader(io.StringIO(content), delimiter=delimiter)
    else:
        f = open(path, newline="")
        reader = csv.reader(f, delimiter=delimiter)
    
    rows = list(reader)
    if path != "-":
        f.close()
    return rows


def calc_widths(rows, max_rows=None):
    widths = []
    display = rows[:max_rows] if max_rows else rows
    for row in display:
        for i, cell in enumerate(row):
            while len(widths) <= i:
                widths.append(0)
            widths[i] = max(widths[i], len(cell))
    return widths


def format_row(row, widths):
    parts = []
    for i, cell in enumerate(row):
        w = widths[i] if i < len(widths) else len(cell)
        parts.append(cell.ljust(w))
    return " │ ".join(parts)


def color_row(row, widths, header=False):
    if header:
        cells = []
        for i, cell in enumerate(row):
            w = widths[i] if i < len(widths) else len(cell)
            cells.append(color(cell.ljust(w), "36;1"))
        return " │ ".join(cells)
    return format_row(row, widths)


def cmd_view(args):
    try:
        rows = read_csv(args.file, delimiter=args.delimiter)
    except FileNotFoundError:
        print(f"Error: File '{args.file}' not found", file=sys.stderr)
        sys.exit(1)
    except Exception as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)
    
    if not rows:
        print(f"{color('(empty)', '90')}")
        return
    
    has_header = not args.no_header and rows
    
    # Filter
    if args.filter:
        col_idx = None
        if "=" in args.filter:
            col_name, val = args.filter.split("=", 1)
            if has_header:
                try:
                    col_idx = rows[0].index(col_name)
                except ValueError:
                    print(f"Error: Column '{col_name}' not found",
                          file=sys.stderr)
                    sys.exit(1)
            else:
                try:
                    col_idx = int(col_name) - 1
                except ValueError:
                    print(f"Error: Invalid column index", file=sys.stderr)
                    sys.exit(1)
            
            if col_idx is not None:
                rows = [rows[0]] + [r for r in rows[1:]
                                    if col_idx < len(r) and val in r[col_idx]]
    
    # Search
    if args.search:
        rows = [rows[0]] + [r for r in rows[1:]
                            if any(args.search.lower() in c.lower()
                                   for c in r)]
    
    # Stats
    if args.stats:
        print(f"\n  {color('CSV Stats', '1')}")
        print(f"  {color('─' * 40, '90')}")
        print(f"  Rows:       {len(rows) - (1 if has_header else 0)}")
        print(f"  Columns:    {len(rows[0]) if rows else 0}")
        if has_header:
            print(f"  Headers:    {', '.join(color(h, '36') for h in rows[0])}")
        if len(rows) > 1:
            print(f"  File size:  {os.path.getsize(args.file) if args.file != '-' else '?'} bytes")
        print()
        return
    
    widths = calc_widths(rows, max_rows=50)
    
    # Truncation message
    max_rows = 500
    if len(rows) > max_rows:
        print(f"{color(f'Showing {max_rows} of {len(rows)} rows. Use --search to narrow.', '33')}")
        rows = rows[:max_rows]
    
    print()
    if has_header:
        print(color_row(rows[0], widths, header=True))
        print(color("─" * (sum(widths) + 3 * len(widths)), "90"))
        data = rows[1:]
    else:
        data = rows
    
    for row in data:
        print(color_row(row, widths))
    
    print(f"\n{color(f'{len(data)} rows', '90')}")
    return


def main():
    parser = argparse.ArgumentParser(
        description="Csvview — CSV/TSV viewer",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=(
            "Examples:\n"
            "  csvview data.csv                   # View CSV\n"
            "  csvview data.tsv --delimiter $'\\t' # View TSV\n"
            "  csvview data.csv --stats           # Show column stats\n"
            "  csvview data.csv --search error    # Search for 'error'\n"
            "  csvview data.csv --filter 'status=active'  # Filter by column\n"
            "  cat data.csv | csvview -           # Pipe input\n"
        ),
    )
    parser.add_argument("file", help="CSV file (use - for stdin)")
    parser.add_argument("--delimiter", default=",",
                        help="Field delimiter (default: ,)")
    parser.add_argument("--no-header", action="store_true",
                        help="File has no header row")
    parser.add_argument("--filter",
                        help="Filter: column=value or col_idx=value")
    parser.add_argument("--search",
                        help="Search term across all columns")
    parser.add_argument("--stats", action="store_true",
                        help="Show column statistics")
    parser.add_argument("--version", action="version",
                        version="csvview 1.0.0")
    
    args = parser.parse_args()
    cmd_view(args)


if __name__ == "__main__":
    main()