from calendar import month_name
import json
import os
import re


def get_sources(db_dir, collection):
    """
    Return the source files for all emails indexed in the database.
    The source file names look like 'R-help/2024-April.txt' and are repeated
    for as many tims as there are indexed emails from each source file.

    Args:
        db_dir: Database directory
        collection: Email collection
    """
    # Path to the JSON Lines file
    file_path = os.path.join(db_dir, collection, "bm25", "corpus.jsonl")

    # Read the JSON Lines file
    with open(file_path, "r", encoding="utf-8") as file:
        # Parse each line as a JSON object
        sources = [json.loads(line.strip())["metadata"]["source"] for line in file]

    return sources


def get_start_end_months(sources):
    """
    Given a set of filenames like 'R-help/2024-January.txt', return the earliest and latest month in 'Month YYYY' format.
    """
    # Get just the file names (e.g. 2024-January.txt)
    filenames = [os.path.basename(source) for source in sources]
    pattern = re.compile(r"(\d{4})-([A-Za-z]+)\.txt")
    months = []
    # Start with the unique filenames
    unique_filenames = set(filenames)
    for src in unique_filenames:
        m = pattern.match(src)
        if m:
            year = int(m.group(1))
            month_str = m.group(2)
            try:
                month_num = list(month_name).index(month_str)
            except ValueError:
                continue
            if month_num == 0:
                continue
            months.append((year, month_num, month_str))
    if not months:
        return None, None
    months.sort()
    start = months[0]
    end = months[-1]
    return f"{start[2]} {start[0]}", f"{end[2]} {end[0]}"