#!/bin/env python

# Simple text-wrapping script for email.
# Preserves code blocks, quotes, and signature.
# Automatically joins and re-wraps paragraphs to
# ensure even spacing & avoid ugly wrapping.
# Preserves signoffs, eg: Yours truly,\nJohn Doe
# Signoff heuristic:
# 1-5 words ending with a comma, followed by
# 1-5 words that each start with capital letters.
# Author: Daniel Fichtinger
# License: MIT

import textwrap
import sys
import re
import argparse

paragraph: list[str] = []
skipping = False
squash = True
prev_is_parbreak = False
out_stream = sys.stdout
reflow = True
width = 74
break_long_words = False
replace_whitespace = True


def pprint(string: str):
    if not squash:
        print(string, file=out_stream)
    else:
        parbreak = not string
        global prev_is_parbreak
        if skipping or not (parbreak and prev_is_parbreak):
            print(string, file=out_stream)
        prev_is_parbreak = parbreak


def wrap(text: str):
    return textwrap.wrap(
        text,
        width=width,
        break_long_words=break_long_words,
        replace_whitespace=replace_whitespace,
    )


def flush_paragraph():
    if paragraph:
        if reflow:
            joined = " ".join(paragraph)
            wrapped = wrap(joined)
            pprint("\n".join(wrapped))
        else:
            for line in paragraph:
                for wrapped_line in wrap(line):
                    pprint(wrapped_line)
        paragraph.clear()


signoff_cache: str = ""


def check_signoff(line: str) -> bool:
    if not line:
        return False
    words = line.split()
    n = len(words)
    # first potential signoff line
    if not signoff_cache and 1 <= n <= 5 and line[-1] == ",":
        return True
    # second potential line
    elif signoff_cache and 1 <= n <= 5 and line[-1].isalpha():
        for w in words:
            if not w[0].isupper():
                return False
        return True
    else:
        return False


if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description='Formatter for plain text email.\n"--no-*" options are NOT passed by default.',
        epilog="""
Author : Daniel Fichtinger
License: MIT
Contact: daniel@ficd.ca
        """,
        formatter_class=argparse.RawDescriptionHelpFormatter,
    )
    parser.add_argument(
        "-w",
        "--width",
        required=False,
        help="Text width for wrapping. (default: %(default)s)",
        default=width,
        type=int,
    )
    parser.add_argument(
        "-b",
        "--break-long-words",
        required=False,
        help="Break long words while wrapping. (default: %(default)s)",
        action="store_true",
    )
    parser.add_argument(
        "--no-replace-whitespace",
        required=False,
        help="Don't normalize whitespace when wrapping.",
        action="store_false",
    )
    parser.add_argument(
        "--no-reflow",
        required=False,
        help="Don't reflow lines.",
        action="store_false",
    )
    parser.add_argument(
        "--no-signoff",
        required=False,
        help="Don't preserve signoff line breaks.",
        action="store_false",
    )
    parser.add_argument(
        "--no-signature",
        required=False,
        help="Don't preserve signature block.",
        action="store_false",
    )
    parser.add_argument(
        "--no-squash",
        required=False,
        help="Don't squash consecutive paragraph breaks.",
        action="store_false",
    )
    parser.add_argument(
        "-i",
        "--input",
        required=False,
        type=str,
        default="STDIN",
        help="Input file. (default: %(default)s)",
    )
    parser.add_argument(
        "-o",
        "--output",
        required=False,
        type=str,
        default="STDOUT",
        help="Output file. (default: %(default)s)",
    )
    args = parser.parse_args()
    width = args.width
    should_check_signoff = args.no_signoff
    should_check_signature = args.no_signature
    reflow = args.no_reflow
    squash = args.no_squash
    replace_whitespace = args.no_replace_whitespace
    break_long_words = args.break_long_words

    if args.input == "STDIN":
        reader = sys.stdin
    else:
        with open(args.input, "r") as in_stream:
            reader = in_stream
    if args.output != "STDOUT":
        out_stream = open(args.output, "w")

    for line in reader:
        line = line.rstrip()
        if should_check_signoff:
            is_signoff = check_signoff(line)
            if is_signoff:
                if not signoff_cache:
                    signoff_cache = line
                else:
                    pprint(signoff_cache)
                    pprint(line)
                    signoff_cache = ""
                continue
            elif not is_signoff and signoff_cache:
                paragraph.append(signoff_cache)
                signoff_cache = ""
        if line.startswith("```"):
            flush_paragraph()
            skipping = not skipping
            pprint(line)
        elif should_check_signature and line == "--":
            flush_paragraph()
            skipping = True
            pprint("-- ")
        elif not line or re.match(
            r"^(\s+|-\s+|\+\s+|\*\s+|>\s*|#\s+|From:|To:|Cc:|Bcc:|Subject:|Reply-To:|In-Reply-To:|References:|Date:|Message-Id:|User-Agent:)",
            line,
        ):
            flush_paragraph()
            pprint(line)
        elif skipping:
            pprint(line)
        else:
            paragraph.append(line)
    else:
        if signoff_cache:
            paragraph.append(signoff_cache)
            signoff_cache = ""
        flush_paragraph()
    if out_stream is not None:
        out_stream.close()

# pyright: basic