import std/[times, os, strutils, strbasics, strscans, sets, re, deques], parseopt

const VERSION = "0.1"
const configDir = expandTilde("~/.config/then/")
const defaultConfigFile = configDir & "then.toml"
const defaultCalendarFile = configDir & "calendar.then"

type
  Token = object
    token: string
    precedence: int

# Creates a default configuration file if it doesn't exist
proc createDefaultConfigFile() =
  if not fileExists(defaultConfigFile):
    if not dirExists(configDir):
      createDir(configDir)
    writeFile(defaultConfigFile, """
    [config]
    directory = "~/.config/then/"
    """)

# Creates a default calendar file if it doesn't exist
proc createDefaultCalendarFile() =
  if not fileExists(defaultCalendarFile):
    if not dirExists(configDir):
      createDir(configDir)
    writeFile(defaultCalendarFile, """
    # Add your events here
    """)

proc printHelp(badCmd: string) =
  if badCmd != "":
    echo badCmd & " is not a valid option\n"
  echo """
Usage:
  then [options] [commands]

OPTIONS
  -h, --help     show list of CLI options
  -v, --version  show then version
  --future=DAYS  set future
  --past=DAYS    set past

COMMANDS
  a              print upcoming agenda (default command)
  e              open default calendar file in $EDITOR
  j              print the modified julian day
  """
  quit()

proc printVersion() =
  echo "then " & VERSION
  quit()

proc checkType(cond: string): string =
  if cond.len == 4 and parseInt(cond) != 0: return "year"
  if cond.len in [1, 2] and parseInt(cond) != 0: return "day"
  if cond in DefaultLocale.MMM.toHashSet or cond in DefaultLocale.MMMM.toHashSet: return "month"
  if cond in DefaultLocale.ddd.toHashSet or cond in DefaultLocale.dddd.toHashSet: return "dayofweek"
  if find(cond, re"\d{1,2}:\d{2}") > -1: return "time"
  if find(cond, re"\dw") > -1: return "firstweek"
  if find(cond, re"\dl") > -1: return "lastweek"
  if find(cond, re"J%\d([-+]\d)?") > -1: return "julian"
  return "unknown"

proc checkCond(cond: string, day: DateTime): bool =
  case checkType(cond):
    of "year":
      if parseInt(cond) == day.year: return true
    of "day":
      if parseInt(cond) == parseInt(day.format("d")): return true
      if parseInt(cond) == parseInt(day.format("dd")): return true
    of "month":
      if cond == day.format("MMM"): return true
      if cond == day.format("MMMM"): return true
    of "dayofweek":
      if cond == day.format("ddd"): return true
      if cond == day.format("dddd"): return true
    of "time":
      return true
    of "firstweek":
      discard
# Uh oh we didn't think about this hard enough

    of "unknown":
      echo "UNKNOWN THING ", cond
  return false

proc getConditions(dateStr: string): seq[string] =
  var conditions: seq[string]
  conditions = dateStr.rsplit(' ')
  return conditions

# TODO simplify?? Would it be easier to identify conditions and replace them with TRUE/FALSE then just process the string?

# Shunting yard to parse conditions, parens, and logical operators
# Does NOT parse out individual conditions yet because some individual
# conditions (like 1W) require context of surrounding conditions.
# The logic around parentheses is a little weird because conditions like
# "<(March 15)" contain parentheses that we don't want to throw out
proc parseDateToEvents(dateStr: string): seq[string] =
  var holdingStack = initDeque[Token]()
  var resultStack = initDeque[Token]()
  var newToken: string = ""
  for c in dateStr:
    echo c
    case c:
      of '(':
        if newToken.len == 1:
          if newToken[0] == '>' or newToken[0] == '<':
            newToken.add(c)
          else
            echo "ERROR: newToken exists but we got an open paren?"
        else:
          holdingStack.addLast(Token(token: "(", precedence: 0))
      of ')':
        if newToken.len > 0: # Closing token like <(March 15). Push the token.
          resultStack.addLast(Token(token: newToken, precedence: 0))
          newToken = ""
        else: # Logical closing paren. Pop stack until (.
          while holdingStack.len > 0 and holdingStack.peekLast.token != "(":
            if holdingStack.len == 0:
              echo "UH OH, ERROR MISMATCHED PARENS"
            resultStack.addLast(holdingStack.popLast)
          discard holdingStack.popLast # Pop the (
      of '!':
        holdingStack.addLast(Token(token: "!", precedence: 3))
      of '|':
        while holdingStack.len > 0 and holdingStack.peekLast.precedence > 2:
          resultStack.addLast(holdingStack.popLast)
        holdingStack.addLast(Token(token: "|", precedence: 2))
      of ' ':
        if newToken.len > 1 and newToken[1] == '(' and newToken[newToken.len-1] != ')': # Middle of token like <(March 15).
          newToken.add(c)
        else: # End of new token, implicit &
          # Add newToken to result
          resultStack.addLast(Token(token: newToken, precedence: 0))
          newToken = ""
          # Add implicit & to holding
          while holdingStack.len > 0 and holdingStack.peekLast.precedence > 1:
            resultStack.addLast(holdingStack.popLast)
          holdingStack.addLast(Token(token:"&", precedence: 1))
      of '>','<',':','-','a'..'z','A'..'Z','0'..'9':
        newToken.add(c)
      else:
        echo "Weird character in dateStr: ", c
        discard
  # Push last token
  if newToken.len > 0:
    resultStack.addLast(Token(token: newToken, precedence: 0))
  # Clear the holding stack
  while holdingStack.len > 0:
    var t = holdingStack.popLast
    if t.token != "(":
      resultStack.addLast(t)
  echo resultStack


proc getEvents(cal: seq[string], day: DateTime): seq[string] =
  var events: seq[string]
  for line in cal:
    var (success, dateStr, eventStr) = scanTuple(line, "$*,$*")
    if success:
      dateStr.strip
      eventStr.strip
      discard parseDateToEvents(dateStr)
      #let conditions = getConditions(dateStr)
    #  var match = true
    #  for c in conditions:
    #    c = c.toLower.capitalizeAscii
    #    if checkCond(c, day) == false:
    #      match = false
    #      break
    #  if match:
    #    events.add(eventStr)
    else:
      echo "WARNING: Cannot parse line: ", line
  return events

proc printEvents(cal: seq[string], day: DateTime) =
  let events = getEvents(cal, day)
  if events.len > 0:
    echo day.format("ddd  yyyy MMM dd")
    for e in events:
      echo " - ", e

proc openCal(file: string): seq[string] =
  let f = open(file)
  var cal: seq[string]
  for line in f.lines:
    cal.add(line)
  f.close()
  return cal

proc printCalendar() =
  let cal = openCal(defaultCalendarFile)
  var past = 3
  var future = 7
  let now = now()

  while past > 0:
    let curDay = now - past.days
    printEvents(cal, curDay)
    dec past

  printEvents(cal, now)

  for i in 1..future:
    let curDay = now + i.days
    printEvents(cal, curDay)

proc main() =
  var   past: int = 1
  var future: int = 14
  var  noArg: bool = true
  for kind, key, val in getopt():
    case kind
    of cmdLongOption, cmdShortOption:
      noArg = false
      case key
      of "help", "h":
        printHelp("")
      of "version", "v":
        printVersion()
      else:
        printHelp(key)
    else:
      discard

  if noArg:
    printCalendar()

when isMainModule:
  main()