import os
import sys
CLI_SEPARATOR = "======================================================================\n"
CLI_HEADER = "\nprocess_forex_csv\nProcesses CSV version of RBA Exchange Rate history:\nhttps://www.rba.gov.au/statistics/historical-data.html#exchange-rates\nfrom supplied format to a format ready for ETL"
CLI_USAGE = "Usage:\nprocess_forex_csv.py [input_filename] [output_filename] [format_as_sql (y/n)] [append_to_output]\n"
OUTPUT_HEADER = "Date,Currency,Rate\n"
FILE_HEADER_1 = "EXCHANGE RATES ,,,,,,,,,,,,,,,,,,,,,,,"
FILE_HEADER_2 = "HISTORICAL DAILY EXCHANGE RATES OF THE AUSTRALIAN DOLLAR AGAINST:"
FOREX_HEADER = "Series ID"
months = {
    "jan": "01",
    "feb": "02",
    "mar": "03",
    "apr": "04",
    "may": "05",
    "jun": "06",
    "jul": "07",
    "aug": "08",
    "sep": "09",
    "oct": "10",
    "nov": "11",
    "dec": "12"
}
def isNull(val): return True if str(val).upper() == 'NULL' else False
class ProcessForexCSV:
    def __init__(self, input_filename, output_filename, format_for_sql, append_to_output):
        self.input_filename = input_filename
        self.output_filename = output_filename
        self.format_for_sql = format_for_sql
        self.append_to_output = append_to_output
        self.currencies = []
    def process_file(self):
        input_file_path = os.path.join(os.getcwd(), self.input_filename)
        output_file_path = os.path.join(os.getcwd(), self.output_filename)
        with open(input_file_path, "rt") as f:
            new_lines = ""
            line = f.readline()
            if line.find(FILE_HEADER_1) < 0 and line.find(FILE_HEADER_2) < 0:
                print("Invalid file format.")
                return
            line = f.readline()
            while line.find(FOREX_HEADER) < 0:
                line = f.readline()
            tokens = line.split(",")
            i = 0
            for token in tokens:
                if i > 0:
                    self.currencies.append(token[len(token)-3:].strip())
                i += 1
            print("Currencies:\n{0}".format(CLI_SEPARATOR))
            for currency in self.currencies:
                print("{0}".format(currency))
            line = f.readline().strip()
            line_count = 0
            while line != "":
                line_count += 1
                line_tokens = line.split(",")
                token_count = len(line_tokens)
                exchg_date = line_tokens[0]
                original_exchg_date = exchg_date
                date_tokens = exchg_date.split("-")
                exchg_date = date_tokens[2] + months[date_tokens[1].lower()].zfill(2) + date_tokens[0].zfill(2)
                i = 1
                if self.format_for_sql and line_count == 1:
                    line = "VALUES\n"
                    new_lines += line
                while i < token_count:
                    if line_tokens[i] == "":
                        line_tokens[i] = "NULL"
                    exchg_line = ""
                    if not self.format_for_sql:
                        exchg_line = "{0},{1},{2}\n".format(original_exchg_date, self.currencies[i-1], line_tokens[i])
                    else:
                        exchg_line = "    ('" + exchg_date + "','" + self.currencies[i-1] + "'," + line_tokens[i] + "),\n"
                    i += 1    
                    if exchg_line != "":
                        #print(exchg_line)
                        new_lines += exchg_line
                line = f.readline().strip()
        f.close()
        # get rid of the final "union all"
        if self.format_for_sql:
            new_lines = new_lines[:len(new_lines)-len(",\n")]
        else:
            new_lines = new_lines[:len(new_lines)-len("\n")]
        #print(new_lines)
        file_mode = "at" if self.append_to_output else "wt"
        with open(output_file_path, file_mode) as f2:
            if not self.format_for_sql and not self.append_to_output:
                f2.write(OUTPUT_HEADER)
            f2.write(new_lines)
        f2.close()
        print("{0}\n{1} exchange rates {2} to {3}\n{4}".format(CLI_SEPARATOR, line_count, "appended" if self.append_to_output else "written", self.output_filename, CLI_SEPARATOR))
if __name__ == "__main__":
    print(CLI_HEADER)
    print(CLI_SEPARATOR)
    print(CLI_USAGE)
    
    if len(sys.argv) == 5:
        input_filename = sys.argv[1]
        output_filename = sys.argv[2]
        format_for_sql = True if str(sys.argv[3]).lower() == "y" else False
        append_to_output = True if str(sys.argv[4]).lower() == "y" else False
        process = ProcessForexCSV(input_filename, output_filename, format_for_sql, append_to_output)
        process.process_file()
    else:
        print("Invalid number of parameters.")