"""
Convert the Amazon reviews dataset to parquet format.

Usage:
    $ make download
    $ python convert.py
"""

import os
import gzip

from glob import glob

import pandas as pd

OUTPUT_DIR = "amazon_reviews_2013"
CHUNK_SIZE = 2000000

CATEGORIES = {
    "Amazon_Instant_Video.txt.gz": "Amazon Instant Video",  # 717,651 reviews
    "Arts.txt.gz": "Arts",  # 27,980 reviews
    "Automotive.txt.gz": "Automotive",  # 188,728 reviews
    "Baby.txt.gz": "Baby",  # 184,887 reviews
    "Beauty.txt.gz": "Beauty",  # 252,056 reviews
    "Books.txt.gz": "Book",  # 12,886,488 reviews
    "Cell_Phones_&_Accessories.txt.gz": "Cell Phone",  # 78,930 reviews
    "Clothing_&_Accessories.txt.gz": "Clothing",  # 581,933 reviews
    "Electronics.txt.gz": "Electronics",  # 1,241,778 reviews
    "Gourmet_Foods.txt.gz": "Gourmet Food",  # 154,635 reviews
    "Health.txt.gz": "Health",  # 428,781 reviews
    "Home_&_Kitchen.txt.gz": "Home & Kitchen",  # 991,794 reviews
    "Industrial_&_Scientific.txt.gz": "Industrial & Scientific",  # 137,042 reviews
    "Jewelry.txt.gz": "Jewelry",  # 58,621 reviews
    "Kindle_Store.txt.gz": "Kindle Store",  # 160,793 reviews
    "Movies_&_TV.txt.gz": "Movie & TV",  # 7,850,072 reviews
    "Musical_Instruments.txt.gz": "Musical Instrument",  # 85,405 reviews
    "Music.txt.gz": "Music",  # 6,396,350 reviews
    "Office_Products.txt.gz": "Office",  # 138,084 reviews
    "Patio.txt.gz": "Patio",  # 206,250 reviews
    "Pet_Supplies.txt.gz": "Pet Supply",  # 217,170 reviews
    "Shoes.txt.gz": "Shoe",  # 389,877 reviews
    "Software.txt.gz": "Software",  # 95,084 reviews
    "Sports_&_Outdoors.txt.gz": "Sports & Outdoor",  # 510,991 reviews
    "Tools_&_Home_Improvement.txt.gz": "Tools & Home Improvement",  # 409,499 reviews
    "Toys_&_Games.txt.gz": "Toy & Game",  # 435,996 reviews
    "Video_Games.txt.gz": "Video Game",  # 463,669 reviews
    "Watches.txt.gz": "Watch",  # 68,356 reviews
}


def to_parquet():
    """
    Convert a single file to parquet
    """
    n_chunks = 0
    train_data = []

    for filename in CATEGORIES:

        for entry in parse_file(filename):
            train_data.append(entry)

            if len(train_data) == CHUNK_SIZE:
                save_parquet(train_data, "train", n_chunks)
                train_data = []
                n_chunks += 1

    if train_data:
        save_parquet(train_data, "train", n_chunks)

    return n_chunks


def save_parquet(data, split, chunk):
    """
    Save data to parquet
    """
    fname = os.path.join(OUTPUT_DIR, f"{split}-{chunk:04d}-of-nchunks.parquet")
    df = pd.DataFrame(data)
    df.to_parquet(fname)


def parse_file(filename):
    """
    Parse a single file
    """
    f = gzip.open(filename, "r")
    entry = {}
    for line in f:
        line = line.decode().strip()
        colon_pos = line.find(":")
        if colon_pos == -1:
            entry["product/category"] = CATEGORIES[filename]
            yield entry
            entry = {}
            continue
        e_name = line[:colon_pos]
        rest = line[colon_pos + 2 :]
        entry[e_name] = rest

    yield entry


def rename_chunks(n_chunks):
    """
    Replace nchunks in filename by the actual number of chunks
    """
    for fname in glob(os.path.join(OUTPUT_DIR, "train-*-of-nchunks.parquet")):
        new_fname = fname.replace("-nchunks", f"-{n_chunks:04d}")
        os.rename(fname, new_fname)


def run():
    """
    Convert all files to parquet
    """
    if not os.path.exists(OUTPUT_DIR):
        os.makedirs(OUTPUT_DIR)

    n_chunks = to_parquet()
    print(f"{n_chunks} chunks saved")

    rename_chunks(n_chunks)


if __name__ == "__main__":
    run()