codex/codex.go

package codex

import (
  "fmt"
  "gopkg.in/yaml.v3"
  "os"
)

type Codex interface {
  init(cfg map[string]interface{})

  ID() string
  Decode(data []byte, pos int, value interface{}) (int, error)

  Encode(data []byte, pos int, value interface{}) (int, error)
}

type CodexStruct struct {
  id      string
  fields  []Codex 
}


func LoadCodex(fileName string) Codex {
	data, err := os.ReadFile(fileName)
	if err != nil {
    panic(fmt.Sprintf("Error read config %s: %s", fileName, err))
	}
  m := make(map[string]interface{})
  err = yaml.Unmarshal(data, &m)
  return parseType(m)
}

func parseType(cfg map[string]interface{}) Codex {
  var c Codex
  if ctype, ok := cfg["type"].(string); ok {
    switch ctype {
    case "struct":
      c = &CodexStruct{}
    case "string":
      c = &CodexString{}
    case "bitmap":
      c = &CodexBitmap{}
    case "llvar":
      c = &CodexLVar{PacketLength: 2}
    case "lllvar":
      c = &CodexLVar{PacketLength: 3}
    default:
      panic(fmt.Sprintf("Unknown type [%s]", ctype))
    }
  } else if cfg["type"] == nil {
    c = &CodexString{}
  } else {
    panic(fmt.Sprintf("Invalid Codex.Type %+v", cfg))
  }
  c.init(cfg)
  return c
}

func (c *CodexStruct) init(cfg map[string]interface{}) {
  if v, ok := cfg["id"].(string); ok {
    c.id = v
  } else {
    panic(fmt.Sprintf("Invalid CodexStruct.ID %+v", cfg))
  }
  if v, ok := cfg["fields"].([]interface{}); ok {
    c.fields = make([]Codex, len(v))
    for i,f := range v {
      if fm, ok := f.(map[string]interface{}); ok {
        c.fields[i] = parseType(fm)
      } else {
        panic(fmt.Sprintf("Invalid field %d %+v", i, f))
      }
    }
  } else {
    panic(fmt.Sprintf("Invalid CodexStruct.Fields %+v", cfg))
  }
}

func (c *CodexStruct) ID() string {
  return c.id
}

func (c *CodexStruct) Decode(data []byte, pos int, value interface{}) (int, error) {
  ppos := pos
  var err error
  for _, f := range c.fields {
    ppos, err = f.Decode(data, ppos, value)
    if err != nil {
      return pos, err
    }
  }
  return ppos, nil
}

func (c *CodexStruct) Encode(data []byte, pos int, value interface{}) (int, error) {
  ppos := pos
  var err error
  for _, f := range c.fields {
    ppos, err = f.Encode(data, ppos, value)
    if err != nil {
      return pos, err
    }
  }
  return ppos, nil
}