#!/usr/bin/python3
# COMP3311 21T3 Ass2 ... progression check for a given student

import sys
import psycopg2
import re
from helpers import *

# define any local helper functions here

### set up some globals

def getMostRecentProgStrm(zid, db):
  cur = db.cursor();
  cur.execute("""
    SELECT program, ST.code
    FROM Students AS S,
      Program_enrolments AS PE,
      Stream_Enrolments AS SE,
      Programs AS P,
      Streams AS ST
    WHERE S.id = %s
      AND PE.student = S.id
      AND SE.partof = PE.id
      AND P.id = PE.program
      AND ST.id = SE.stream
    ORDER BY term DESC
  """, [zid]);
  info = cur.fetchone();
  cur.close();
  if not info:
    return None
  else:
    return info

def getRequirements(prog_code, strm_code, db):
  cur = db.cursor();
  cur.execute("""
  SELECT R.name, R.min_req, R.max_req, R.type, AOG.definition, AOG.defby, 1 AS IS_PROG, R.id
  FROM Streams AS S, Stream_Rules AS SR, Rules AS R, Academic_Object_groups AS AOG
  WHERE S.code = %s
      AND SR.stream = S.id
      AND SR.rule = R.id
      AND AOG.id = R.ao_group
  UNION
  SELECT R.name, R.min_req, R.max_req, R.type, AOG.definition, AOG.defby, 0 AS IS_PROG, R.id
  FROM Program_Rules as PR, Rules as R, Academic_Object_Groups AS AOG
  WHERE PR.program = %s
      AND R.id = PR.rule
      AND AOG.id = R.ao_group
      AND AOG.type != 'stream'
  ORDER BY IS_PROG DESC, id ASC
  """, [strm_code, prog_code]);
  info = cur.fetchall();
  cur.close();
  if not info:
    return None
  else:
    return list(info)


def maybeRemovePatternRequirement(requirement, course_code, UOC):
  (name, min_req, max_req, type, definition, defby, stream, aogtype) = requirement

  if type == "FE":
    if requirement[1] != None:
      requirement[1] = requirement[1] - UOC
    if requirement[2] != None:
      requirement[2] = requirement[2] - UOC
    return True

  for subject in definition.split(","):
    match = True
      
    if len(subject) < 2:
        continue

    #print(f"testing {subject} against {course_code}")

    for i in range(0, len(subject)):
      if subject[i] != '#' and course_code[i] != subject[i]:
        match = False
        break

    if match == True:
      if requirement[1] != None:
        requirement[1] = requirement[1] - UOC
      if requirement[2] != None:
        requirement[2] = requirement[2] - UOC

      if not '#' in subject:
        requirement[4] = requirement[4].replace(subject, "")
      return True;

  return False


def maybeRemoveEnumRequirement(requirement, course_code):
  removeStr = None;
  (name, min_req, max_req, type, definition, defby, stream, aogtype) = requirement
  for subject in definition.split(","):
    subject = subject.replace("{", "")
    subject = subject.replace("}", "")
    for code in subject.split(";"):
      if code == course_code:
        removeStr = subject
        break
    if removeStr != None:
      break

  if removeStr == None:
    return False 

  requirement[4] = requirement[4].replace(removeStr, "")
  return True


def maybeRemoveInnerRequirement(requirement, course_code, UOC):
  (name, min_req, max_req, type, definition, defby, stream, aogtype) = requirement
  if defby == "pattern":
    return maybeRemovePatternRequirement(requirement, course_code, UOC)
  elif defby == "enumerated":
    return maybeRemoveEnumRequirement(requirement, course_code)


def shouldPopPattern(requirement):
  (name, min_req, max_req, type, definition, defby, stream, aogtype) = requirement
  if min_req != None and min_req <= 0:
    return True
  if max_req != None and max_req <= 0:
    return True
  return any(l.isalnum() for l in definition) == False


def maybeRemoveRequirement(requirements, course_code, UOC):
  removeIndex = None

  if removeIndex == None:
    for count, requirement in enumerate(requirements):
      (name, min_req, max_req, type, definition, defby, stream, _) = requirement

      if stream == 1: 
        continue

      if type == "FE":
        continue # handled in next loop

      #print(f"checking against {name} : { maybeRemoveInnerRequirement(requirement, course_code, UOC)}")
      if maybeRemoveInnerRequirement(requirement, course_code, UOC):
        removeIndex = count
        break

  if removeIndex == None:
    for count, requirement in enumerate(requirements):
      (name, min_req, max_req, type, definition, defby, stream, _) = requirement

      if stream == 0:
        continue
      
      if type == "FE":
        continue # handled in next loop


      if maybeRemoveInnerRequirement(requirement, course_code, UOC) == True:
        removeIndex = count
        break


  # Special FE case, they should be prioritised last.
  isFreeElective = False # For some reason we only return Free Electives here
  if removeIndex == None:
    for count, requirement in enumerate(requirements):
      (name, min_req, max_req, type, definition, defby, stream, _) = requirement

      if type != "FE":
        continue # handled in next loop

      if maybeRemoveInnerRequirement(requirement, course_code, UOC) == True:
        removeIndex = count
        isFreeElective = True
        break

  if removeIndex == None:
    return None

  # Remove if our min_req is zero for pattern, or if we have nothing else to 
  # enumerate in requirements. 
  (name, min_req, max_req, type, definition, defby, stream, _) = requirements[removeIndex];
  if defby == "pattern":
    if shouldPopPattern(requirement):
      requirements.pop(removeIndex)
  elif defby == "enumerated":
    if any(l.isalnum() for l in definition) == False:
      requirements.pop(removeIndex)

  return name if isFreeElective == False else "Free Electives"


def printAcademicRequirementsType(requirements, expected_type, db):
    for requirement in requirements:
      (name, min_req, max_req, type, definition, defby, stream, aogtype) = requirement
      
      if type != expected_type:
        continue

      def_count = str.count(definition, ",")
      if type == "DS":
        print(f"{min_req} stream(s) from {name}")
        printStreams(definition, db)

      elif type == "CC" or type == "PE" and min_req:
        if defby == "pattern":
          print(getCountString(def_count, min_req, max_req, name))
          continue
        printSubjects(definition, defby, db)

      elif type == "GE" and min_req:
        print(f"{min_req} UOC of {name}")

      elif type == "FE" and min_req:
        print(f"at least {min_req} UOC of Free Electives")

      #else:
      #  print(f"UNEXPECTED {name}, {min_req}, {max_req}, {type}, {defby}")


def printAcademicRequirements(requirements, db):
  printAcademicRequirementsType(requirements, "CC", db)
  printAcademicRequirementsType(requirements, "PE", db)
  printAcademicRequirementsType(requirements, "GE", db)
  printAcademicRequirementsType(requirements, "FE", db)
  

usage = f"Usage: {sys.argv[0]} zID [Program Stream]"
db = None

### process command-line args

argc = len(sys.argv)
if argc < 2:
  print(usage)
  exit(1)
zid = sys.argv[1]
if zid[0] == 'z':
  zid = zid[1:8]
digits = re.compile("^\d{7}$")
if not digits.match(zid):
  print("Invalid student ID")
  exit(1)

progCode = None
strmCode = None

if argc == 4:
  progCode = sys.argv[2]
  strmCode = sys.argv[3]

# manipulate database

try:
  db = psycopg2.connect("dbname=mymyunsw")
  stuInfo = getStudent(db,zid)
  if not stuInfo:
    print(f"Invalid student id {zid}")
    exit()

  if progCode == None or strmCode == None:
    (pc, sc) = getMostRecentProgStrm(zid, db)
    progCode = str(pc)
    strmCode = str(sc)

  progInfo = getProgram(db,progCode)
  if progCode:
    if not progInfo:
      print(f"Invalid program code {progCode}")
      exit()

  strmInfo = getStream(db,strmCode)
  if strmCode:
    if not strmInfo:
      print(f"Invalid program code {strmCode}")
      exit()

  print(f"{stuInfo[0]} {stuInfo[1]}, {stuInfo[2]}")
  print(f"  {progInfo[0]} {progInfo[1]}")
  print(f"  {strmCode} {strmInfo[0]}");

  # Our general strategy is threefold:
  # 1. Generate a data structure containing all the requirements of the degree
  # 2. Iterate and print all completed subjects, while removing requirements 
  #    from (1) if fulfilled.
  # 3. Print the remainder of (1), or ready to graduate if empty.
  requirements = list(getRequirements(progCode, strmCode, db))
  requirements = [list(a) for a in requirements]

  print("\nCompleted:")

  total_uoc = 0
  for (CourseCode, Term, SubjectTitle, Mark, Grade, UOC) in getStudentCourses(db, zid):

    remove_requirement_str = maybeRemoveRequirement(requirements, CourseCode, UOC) if doesGradeAddUOC(Grade) else None
    mark_str = Mark if Mark != None else "-"

    total_uoc += UOC if doesGradeAddUOC(Grade) and remove_requirement_str != None else 0

    uoc_str = " " + getGradeString(Grade) if getGradeString(Grade) != "Xuoc" else f"{UOC:2d}uoc"
    if remove_requirement_str != None:
      uoc_str = uoc_str + f" towards {remove_requirement_str}"
    elif doesGradeAddUOC(Grade) == False:
      uoc_str = uoc_str + " does not count"
    else:
      uoc_str = " 0uoc does not satisfy any rule"

    print(f"{CourseCode} {Term} {SubjectTitle :<32s}{mark_str :>3} {Grade :>2s}  {uoc_str}")

  print(f"UOC = {total_uoc} so far")

  if len(requirements) > 0:
    print("\nRemaining to complete degree:")
    printAcademicRequirements(requirements, db)
  else:
    print("Eligible to graduate")

except Exception as err:
  print("DB error: ", err)
finally:
  if db:
    db.close()