import strformat
import strutils

import value

type
  OpCode* = enum
    opReturn, opCall, # functions
    opPop, # pop
    opPrint, # print
    opNegate, opNot # unary
    opAdd, opSubtract, opMultiply, opDivide, # math
    opEqual, opGreater, opLess, # comparison
    opTrue, opFalse, opNil, # literal
    opConstant, # constant
    opDefineGlobal, opGetGlobal, opSetGlobal, # globals (uses constants)
    opGetLocal, opSetLocal, # locals
    opJumpIfFalse, opJump, opLoop, opJumpIfFalsePop, # jumps

  Chunk* = object
    code*: seq[uint8]
    constants*: seq[KonValue]
    lines*: seq[int]
    name*: string # name of the module/chunk/files

  Triple* = array[3, uint8]

proc initChunk*(name: string): Chunk =
  Chunk(code: @[], name: name, lines: @[], constants: @[])

proc writeChunk*(ch: var Chunk, code: uint8, line: int) =
  ch.code.add(code)
  ch.lines.add(line)

proc writeChunk*(ch: var Chunk, code: OpCode, line: int) =
  ch.code.add(code.uint8)
  ch.lines.add(line)

proc writeChunk*(ch: var Chunk, code: Triple, line: int) =
  for c in code:
    ch.code.add(c)
    ch.lines.add(line)

proc len*(ch: Chunk): int =
  ch.code.len

proc toTriple*(integer: int): Triple =
  var integer = integer
  result[0] = integer.uint8
  integer = integer div 256
  result[1] = integer.uint8
  integer = integer div 256
  result[2] = integer.uint8

proc toInt*(triple: Triple): int =
  triple[0].int + triple[1].int * 256 + triple[2].int * 256 * 256

proc addConstant*(ch: var Chunk, constant: KonValue): int =
  ch.constants.add(constant)
  ch.constants.high

proc writeConstant*(ch: var Chunk, constant: KonValue, line: int): int =
  result = ch.addConstant(constant)
  ch.writeChunk(opConstant, line)
  ch.writeChunk(result.toTriple, line)

const simpleInstructions = {
  opReturn,
  opPop,
  opPrint,
  opNegate, opNot,
  opAdd, opSubtract, opMultiply, opDivide,
  opEqual, opGreater, opLess,
  opTrue, opFalse, opNil
}
const constantInstructions = {
  opConstant,
  opDefineGlobal, opGetGlobal, opSetGlobal,
}
const argInstructions = {
  opCall,
  opGetLocal, opSetLocal,
  opJumpIfFalse, opJump, opLoop, opJumpIfFalsePop,
}

const tripleMax*: int = 16777215

proc disassembleChunk*(ch: Chunk) =
  echo &"== Chunk {ch.name} begin =="
  echo "index  line instruction"
  var c: int = 0
  var lastLine = -1
  while c < ch.code.len:
    template instruction: uint8 = ch.code[c]
    template line: int = ch.lines[c]
    template triple: Triple = [ch.code[c+1], ch.code[c+2], ch.code[c+3]]
    let cFmt = &"{c:04}"
    let lineFmt =  if lastLine == line: "  | " else: &"{line:04}"
    try:
      write stdout, &"[{cFmt}] {lineFmt} {instruction.OpCode} ({instruction.toHex(2)}"
      case instruction.OpCode:
        of simpleInstructions:
          write stdout, ")\n"
        of argInstructions:
          write stdout, &" {triple[0].toHex(2)} {triple[1].toHex(2)} {triple[2].toHex(2)})\n"
          c += 3
        of constantInstructions:
          let i = triple.toInt
          write stdout, &" {triple[0].toHex(2)} {triple[1].toHex(2)} {triple[2].toHex(2)})\n"
          echo &"            points to constant {ch.constants[i]} (i: {i})"
          c += 3
    except:
      echo &"[{cFmt}] {lineFmt} Unknown opcode {instruction}"
    c.inc
  echo &"== Chunk {ch.name} end =="