You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 

306 lines
8.4 KiB

/*
Copyright (c) 2021 Arsen Musayelyan
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
*/
// Package scpt provides an interpreter for my simple applescript-like
// scripting language
package scpt
import (
"errors"
"fmt"
"github.com/alecthomas/participle"
"github.com/antonmedv/expr"
"io"
"reflect"
"strings"
)
// AddFuncs adds all functions from the provided FuncMap into
// the Funcs variable
func AddFuncs(fnMap FuncMap) {
// Add each function to Funcs
for name, fn := range fnMap {
Funcs[name] = fn
}
}
// AddVars adds all functions from the provided map into
// the Vars variable
func AddVars(varMap map[string]interface{}) {
for name, val := range varMap {
// Add each variable to Vars
Vars[name] = val
}
}
// Parse uses participle to parse a script from r into a new AST
func Parse(r io.Reader) (*AST, error) {
// Build parser from empty AST struct with custom lexer
parser, err := participle.Build(
&AST{},
participle.Lexer(scptLexer),
participle.Elide("Whitespace", "Comment"),
)
if err != nil {
return nil, err
}
// Create new empty AST struct
ast := &AST{}
// Parse script from provided reader into ast
err = parser.Parse(r, ast)
if err != nil {
return nil, err
}
// Return filled AST struct
return ast, nil
}
// ParseValue parses a Value struct into a go value
func ParseValue(val *Value) (interface{}, error) {
// Determine which value was provided and return it
if val.String != nil {
// Return unquoted string
return strings.Trim(*val.String, `"`), nil
} else if val.Bool != nil {
// Return dereferenced Bool converted to bool
return bool(*val.Bool), nil
} else if val.Number != nil {
// Return dereferenced float
return *val.Number, nil
} else if val.SubCmd != nil {
// Return reference to subcommand
return val.SubCmd, nil
} else if val.VarVal != nil {
// If variable access contains index
if val.VarVal.Index != nil {
// Get index value
index, err := callIfFunc(ParseValue(val.VarVal.Index))
if err != nil {
return nil, err
}
// Get requested variable and attempt to assert as []interface{}
slc, ok := Vars[*val.VarVal.Name].([]interface{})
// If assertion successful
if ok {
// Attempt to assert index as a 64-bit float
indexFlt, ok := index.(float64)
if !ok {
return nil, errors.New("array index must be a number")
}
// If requested index is out of range, return error
if int64(len(slc)) <= int64(indexFlt) {
return nil, fmt.Errorf("index %d is out of range with length %d", *val.VarVal.Index, len(slc))
}
// Return value at requested index of requested variable
return slc[int64(indexFlt)], nil
} else {
// If assertion unsuccessful, attempt to assert as a map[interface{}]interface{}
iMap, ok := Vars[*val.VarVal.Name].(map[interface{}]interface{})
if !ok {
return nil, errors.New("variable " + *val.VarVal.Name + " does not exist or is not a map")
}
// Attempt to get value at requested key
val, ok := iMap[index]
if !ok {
return nil, fmt.Errorf("index %v does not exist in map", index)
}
// Return value at key with no error
return val, nil
}
} else {
// If index is absent, attempt to get variable value from Vars
value, ok := Vars[*val.VarVal.Name]
if !ok {
return nil, errors.New("variable " + *val.VarVal.Name + " does not exist")
}
// Return value with no error
return value, nil
}
} else if val.Expr != nil {
// If value is an expression, return evaluated expression
return evalExpr(*val.Expr)
} else if val.Array != nil {
// If value is an array, create new nil []interface{}
var iSlice []interface{}
// For each value in array
for _, value := range val.Array {
// Recursively parse value
iVal, err := callIfFunc(ParseValue(value))
if err != nil {
return nil, err
}
// Append value to []interface{}
iSlice = append(iSlice, iVal)
}
// Return []interface{]
return iSlice, nil
} else if val.Map != nil {
// If value is a map, create new empty map[interface{}]interface{}
iMap := map[interface{}]interface{}{}
// For each value in map
for _, value := range val.Map {
// Recursively parse value
iVal, err := ParseValue(value.Value)
if err != nil {
return nil, err
}
// Recursively parse key
iKey, err := ParseValue(value.Key)
if err != nil {
return nil, err
}
// Set key of map to value
iMap[iKey] = iVal
}
// Return map[interface{}]interface{}
return iMap, nil
}
return nil, nil
}
// Evaluate given expression, returning its value and optionally an error
func evalExpr(expression Expression) (interface{}, error) {
// Parse value of left side of expression
left, _ := callIfFunc(ParseValue(expression.Left))
// If value is string, requote
if isStr(left) {
left = quoteStr(left.(string))
}
// Create new nil string
var right string
// For every right gsegment
for _, segment := range expression.RightSegs {
// Parse value of right segment, calling it if it is a function
rVal, _ := callIfFunc(ParseValue(segment.Right))
// If value is string, requote
if isStr(rVal) {
rVal = quoteStr(rVal)
}
// Append right segment to right string
right = right + fmt.Sprintf(
" %s %v",
segment.Op,
rVal,
)
}
// Create string expression from segments and operator
exp := fmt.Sprintf(
"%v %s",
left,
right,
)
// Compile string expression
program, err := expr.Compile(strings.ReplaceAll(exp, "^", "**"))
if err != nil {
return nil, err
}
// Run expression
out, err := expr.Run(program, Vars)
if err != nil {
return nil, err
}
// Return expression output value
return out, nil
}
// Add quotes to an unquoted string
func quoteStr(s interface{}) string {
// If s is nil
if s == nil {
// Return empty quotes
return `""`
} else {
// Otherwise return formatted string using %v (any value)
return fmt.Sprintf(`"%v"`, s)
}
}
// Check if i is a string
func isStr(i interface{}) bool {
if i == nil {
return true
}
// if type of input is string, return true
if reflect.TypeOf(i).String() == "string" {
return true
}
return false
}
// Call val if it is a function, otherwise pass through return values
func callIfFunc(val interface{}, err error) (interface{}, error) {
if err != nil {
return nil, err
}
// If val is a pointer to a FuncCall
if IsFuncCall(val) {
// Pass through return values of function call
return CallFunction(val.(*FuncCall))
}
// Return given value
return val, nil
}
// UnwrapArgs takes a slice of Arg structs and returns a map
// storing the argument name and its value. If the argument has
// no name, its key will be an empty string
func UnwrapArgs(args []*Arg) (map[string]interface{}, error) {
// Create new empty map of strings to any type
argMap := map[string]interface{}{}
// For each argument
for _, arg := range args {
// Parse value into interface{}
val, err := ParseValue(arg.Value)
if err != nil {
return nil, err
}
// If value is function call
if IsFuncCall(val) {
// Call function, setting its value as the argument's value
argMap[arg.Key], err = CallFunction(val.(*FuncCall))
if err != nil {
return nil, err
}
// Skip further code and start next loop
continue
}
// Set argument value to parsed value
argMap[arg.Key] = val
}
// Return map of arguments
return argMap, nil
}
// IsFuncCall checks if val is a FuncCall struct
func IsFuncCall(val interface{}) bool {
// If type of val is a pointer to FuncCall, return true
return reflect.TypeOf(val) == reflect.TypeOf(&FuncCall{})
}
// CallFunction executes a given function call in the form of
// a FuncCall struct
func CallFunction(call *FuncCall) (interface{}, error) {
// Unwrap provided arguments
argMap, err := UnwrapArgs(call.Args)
if err != nil {
return nil, err
}
// Attempt to get function from Funcs map
fn, ok := Funcs[call.Name]
if !ok {
return nil, errors.New("no such function: " + call.Name)
}
// Return value received from function
return fn(argMap)
}