package main

import (
	"flag"
	"fmt"
	"os"
  "image"
  "image/color"
	"path/filepath"
	"strings"
	"tildegit.org/sloum/filtress/parser"
)

type point struct {
	x    int
	y    int
	maxX int
	maxY int
}

type filter struct {
	max int
	min int
	val int
}

type filterState struct {
	red      filter
	green    filter
	blue     filter
	alpha    filter
	location point
	mode     filter
}
var variables = map[string]int{}
var tree parser.AST
var fil  filterState
var im   *image.RGBA
var imFormat  string

func openFileFromPath(path string) *os.File {
	file, err := os.Open(path)
	if err != nil {
		panic(err)
	}

	return file
}

func generateAST(path string) {
	filterFile := openFileFromPath(path)
  defer filterFile.Close()
	parser := parser.NewParser(filterFile)
	tree = parser.Parse()
}

func validateInput(path string) {
  generateAST(path)
	if len(tree.Loops) > 0 {
		fmt.Printf("File has %d procedures\n", len(tree.Loops))
		fmt.Println("File is valid")
	} else {
		fmt.Println("Invalid or empty input file")
	}

  os.Exit(0)
}

func filterImage(path, fname string) {
  fmt.Print("Loading image          \r")
  im, imFormat = loadImage(path)
  imSize := im.Bounds().Size()
  variables["WID"] = imSize.X
  variables["HIG"] = imSize.Y
  variables["REG"] = 0
  fil = filterState{
    filter{255, 255, 255},
    filter{255,255,255},
    filter{255,255,255},
    filter{255,255,255},
    point{0,0,imSize.X,imSize.Y},
    filter{3,0,0},
  }

  fmt.Print("Filtering image      \r")
  for _, loop := range tree.Loops {
    for ;loop.Counter > 0; loop.Counter-- {
      for _, proc := range loop.Procedures {
        procedure(proc)
      }
    }
  }
  fmt.Print("Saving image         \n")
  saveImage(path, fname, imFormat, im)
}

func updateRegister(exp parser.Expression) {
  opand := exp.Opperand
  if exp.Variable != "" {
    opand = variables[exp.Variable]
  }
  switch exp.Opperator {
  case '+':
    variables["REG"] += opand
  case '-':
    variables["REG"] -= opand
  case '*':
    variables["REG"] *= opand
  case '/':
    if opand == 0 {
      variables["REG"] = 1
    } else {
      variables["REG"] /= opand
    }
  case '=':
    variables["REG"] = opand
  }
}

func procedure(p parser.Procedure) {
  switch p.Kind {
  case "LOC":
    if len(p.Expressions) == 2 {
      fil.location.update(p.Expressions)
    }
  case "MOD":
    if len(p.Expressions) >= 1 {
      fil.mode.update(p.Expressions[0])
    }
  case "REG":
    if len(p.Expressions) >= 1 {
      updateRegister(p.Expressions[0])
    }
  case "APY":
    applyToImage(p.Expressions)
  case "RED":
    if len(p.Expressions) >= 1 {
      fil.red.update(p.Expressions[0])
    }
  case "BLU":
    if len(p.Expressions) >= 1 {
      fil.blue.update(p.Expressions[0])
    }
  case "GRN":
    if len(p.Expressions) >= 1 {
      fil.green.update(p.Expressions[0])
    }
  case "APH":
    if len(p.Expressions) >= 1 {
      fil.alpha.update(p.Expressions[0])
    }
  case "COL":
    if len(p.Expressions) == 4 {
      fil.red.update(p.Expressions[0])
      fil.green.update(p.Expressions[1])
      fil.blue.update(p.Expressions[2])
      fil.alpha.update(p.Expressions[3])
    }
  }
}

func applyToImage(exps []parser.Expression) {
  if len(exps) == 0 {
    im.SetRGBA(
      fil.location.x,
      fil.location.y,
      color.RGBA{
        uint8(fil.red.val),
        uint8(fil.green.val),
        uint8(fil.blue.val),
        uint8(fil.alpha.val),
      })
  } else if len(exps) == 2 {
    endX := exps[0].Opperand
    endY := exps[1].Opperand
    if exps[0].Variable != "" {
      endX = variables[exps[0].Variable]
    }
    if exps[1].Variable != "" {
      endY = variables[exps[1].Variable]
    }
    endX = getBoxBound(fil.location.x, endX, variables["WID"], exps[0].Opperator)
    endY = getBoxBound(fil.location.y, endY, variables["HIG"], exps[0].Opperator)
    for y := fil.location.y; y <= endY; y++ {
      for x := fil.location.x; x <= endX; x++ {
        im.SetRGBA(
          x,
          y,
          color.RGBA{
            uint8(fil.red.val),
            uint8(fil.green.val),
            uint8(fil.blue.val),
            uint8(fil.alpha.val),
          })
      }
    }
  }
}

func getBoxBound(start, end, max int, op rune) int {
  var out int
  switch op {
  case '+':
    out = start + end
  case '-':
    out = start - end
  case '*':
    out = start * end
  case '/':
    if end == 0 {
      out = 0
    } else {
      out = start / end
    }
  case '%':
    if end == 0 {
      out = 0
    } else {
      out = start % end
    }
  case '=':
    out = start
  }
  if out > max {
    out = max
  } else if out < 0 {
    out = 0
  }
  return out
}


func main() {
  validateFlag := flag.Bool("v", false, "If present, will validate the provided frs file and exit")
  inputFlag := flag.String("image", "", "Path to the image to be filtered")
	flag.Parse()
	posArgs := flag.Args()
	if len(posArgs) > 1 || len(posArgs) < 1 {
		panic(fmt.Sprintf("Input error: Too many positional arguments. Expected one, received %d", len(flag.Args())))
	}
	fpath := posArgs[0]
	fext := strings.ToUpper(filepath.Ext(fpath))
	_, fname := filepath.Split(fpath)

	if fext != ".FRS" {
		panic(fmt.Sprintf("Input error: Incorrect filetype. Expected .FRS, received \".%s\"", fext))
	}

  if *validateFlag {
    fmt.Printf("Validating file: %s ...\n", fname)
    validateInput(fpath)
  }

  if *inputFlag == "" {
    fmt.Println("Input error: No image file was provided to filtress")
    os.Exit(1)
  }

  fmt.Printf("Parsing file: %s ...\n", fname)
  generateAST(fpath)
  frsName := strings.Split(fname, ".")[0]
  filterImage(*inputFlag, frsName)
}