#! /usr/bin/python3
# Last edited on 2026-01-21 22:26:32 by stolfi

# Library function that reads a table that maps strings to strings.
# To be imported by python programs.

from process_funcs import basic_line_loop
import re
from sys import stderr as err

def read_table(fname,invert,verbose):
  # Reads the contents of the table {tbl} from file {fname}. 
  # Returns the table as a python {dict}.
  
  # Blank lines and #-comments in file {fname} are ignored. Each data
  # line must have two non-blank fields {X} and {Y}, separated by one or
  # more blanks. The fields cannot have embedded blanks.
  
  # If {invert} is false, {tbl[X]} is set to {Y}. If {invert} is true, the two fields
  # are conceptually reversed, that is, {tbl[Y]} is set to {X}.
  
  # If {verbose} is true, prints a summary of entries read.
  
  tbl = dict()
    
  def process_line(nread, line):
    nonlocal tbl
    line = line.strip()
    if re.match(r"^[ \011]*([#]|$)", line): return
    line = re.sub(r"[ \011]*[#].*$", "", line)
    fld = re.split(r"[ \011]+", line)
    if len(fld) != 2:
      err.write(f"{fname}:{nread}: ** bad field count\n  [[{line}]]\n")
      sys.exit(1)
    if invert:
      x, y = fld[1], fld[0] 
    else:
      x, y = fld[0], fld[1]
    if x in tbl:
      err.write(f"{fname}:{nread}: ** repeated key = {x}\n  [[{line}]]\n")
      sys.exit(1)
    tbl[x] = y
    return
    # ....................................................................
    
  rd = open(fname, "r")
  nread = basic_line_loop(rd, process_line)
  if len(tbl) == 0:
    err.write(f"{fname}:{nread}: ** no entries in table file {fname}\n [[{line}]]\n")
    sys.exit(1)
  if verbose:
    err.write("loaded {len(tbl)} pairs from {fname}\n")
  rd.close()
  return tbl
  # ----------------------------------------------------------------------