#!/usr/bin/env python3

import json, sys, os, csv

infile    = ""
outfile   = ""
separator = ","
quote     = '"'

nofirstrow = False

EXIT_SUCCESS=0
EXIT_USAGE=1
EXIT_RUNTIME=2

if len(sys.argv)<2 or len(sys.argv)>3:
  sys.stderr.write(
"Usage: "+sys.argv[0]+""" INFILE [OUTFILE]

  INFILE: input file, CSV
  OUTFILE (optional): output file, JSON

Environment Variables:

  SEPARATOR: field delimiter, default comma
  QUOTE: used to quote strings containing SEPARATOR, default '"'
  NOFIRSTROW: true or false, disables using the first row as table headers,
              default false
"""
  )
  sys.stderr.flush()
  sys.exit(EXIT_USAGE)

if os.path.isfile(sys.argv[1]):
  infile = sys.argv[1]
else:
  print("Not a file: "+sys.argv[1], file=sys.stderr)
  sys.exit(EXIT_RUNTIME)

# manually specified name
if len(sys.argv)>2:
  # check if parent directory of specified file exists
  if os.path.isdir(os.path.abspath(os.path.join(sys.argv[2], os.pardir))):
    outfile = sys.argv[2]
  else:
    print("Missing parent dir for: "+sys.argv[2], file=sys.stderr)
    sys.exit(EXIT_RUNTIME)

# attempt to automatically determine name
else:
  if len(sys.argv[1])>4 and sys.argv[1][-4:]==".csv":
    outfile = sys.argv[1][:-4]+".json"
  else:
    print("Cannot automatically determine destination file name for: "+sys.argv[1], file=sys.stderr)
    sys.exit(EXIT_RUNTIME)
  if os.path.exists(outfile):
    print("Destination file exists, refusing to operate: "+outfile, file=sys.stderr)
    print("To overwrite, explicitly specify destination filename on the command line.")
    sys.exit(EXIT_RUNTIME)

separator = os.environ.get("SEPARATOR", ",")
if len(separator)>1:
  print("Warning: Separator from environment appears to be longer than one character. This might cause issues.")

quote = os.environ.get("QUOTE", '"')
if len(quote)>1:
  print("Warning: Quote from environment appears to be longer than one character. This might cause issues.")

if os.environ.get("NOFIRSTROW", "false").lower() == "false":
  nofirstrow = False
elif os.environ["NOFIRSTROW"].lower() == "true":
  nofirstrow = True
else:
  print("Environment variable NOFIRSTROW is set but neither true nor false.", file=sys.stderr)
  sys.exit(EXIT_USAGE)

infileobject = open(infile, "r")
csvreader = csv.reader(infileobject, delimiter=separator, quotechar=quote)

columns = []
rows = []
for row in csvreader:
  if columns == []:
    # assume we are reading the first row
    if nofirstrow:
      columns = list(range(len(row)))
    else:
      columns = row
      continue

  rows = rows + [{}]

  i = 0
  while i<len(columns):
    rows[-1][columns[i]] = row[i]
    i = i+1

infileobject.close()

outfileobject = open(outfile, "w");
outfileobject.write(json.dumps(rows))
outfileobject.close()