scpt/ast.go

package scpt

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"github.com/alecthomas/participle/lexer"
)

var loopRunning bool
var breakLoop bool
var funcRunning bool
var retValue interface{} = nil

// AST stores the root of the Abstract Syntax Tree for scpt
type AST struct {
	Pos      lexer.Position
	Commands []*Command `@@*`
}

// Execute traverses the AST and executes any commands, it returns an error
// containing the position at which the error was encountered and the error
// itself
func (ast *AST) Execute() error {
	// For each command in AST
	for _, cmd := range ast.Commands {
		// Execute current command
		err := executeCmd(cmd)
		if err != nil {
			return err
		}
	}
	return nil
}

func (ast *AST) Dump() ([]byte, error) {
	return json.Marshal(ast)
}

func (ast *AST) DumpPretty() ([]byte, error) {
	buf := bytes.NewBuffer([]byte{})
	enc := json.NewEncoder(buf)
	enc.SetIndent("", "    ")
	err := enc.Encode(ast)
	if err != nil {
		return buf.Bytes(), err
	}
	return buf.Bytes(), nil
}

func LoadAST(data []byte) (*AST, error) {
	var ast AST
	err := json.Unmarshal(data, &ast)
	if err != nil {
		return nil, err
	}
	return &ast, nil
}

// Execute a variable declaration
func executeVarCmd(Var *Var) error {
	// Parse value of variable
	val, err := ParseValue(Var.Value)
	if err != nil {
		return fmt.Errorf("%s: %s", Var.Value.Pos, err)
	}
	// If value of variable is a function call
	if IsFuncCall(val) {
		// Assert type of val as *FuncCall
		Call := val.(*FuncCall)
		// Set variable value to function return value
		Vars[Var.Key], err = CallFunction(Call)
		if err != nil {
			return fmt.Errorf("%s: %s", Var.Value.Pos, err)
		}
	} else if Var.Index != nil {
		// If variable definition has an associated index, get index value
		index, err := callIfFunc(ParseValue(Var.Index))
		if err != nil {
			return fmt.Errorf("%s: %s", Var.Index.Pos, err)
		}
		// Attempt to get the variable from Vars and assert it as a []interface{}
		slc, ok := Vars[Var.Key].([]interface{})
		// If assertion successful
		if ok {
			// Assert index value as a 64-bit float
			indexInt, ok := index.(float64)
			if !ok {
				return fmt.Errorf("%s: %s", Var.Pos, "variable "+Var.Key+" does not exist or is not an array")
			}
			// Set integer index of interface{} slice to value
			slc[int64(indexInt)] = val
		} else {
			// If slice assertion unsuccessful, attempt to assert as map[interface{}]interface{}
			iMap, ok := Vars[Var.Key].(map[interface{}]interface{})
			if !ok {
				return fmt.Errorf("%s: %s", Var.Pos, "variable "+Var.Key+" does not exist or is not a map")
			}
			// Set index of interface{} to interface{} map to value
			iMap[index] = val
		}
	} else {
		// If value is not a function call, set variable to parsed value
		Vars[Var.Key] = val
	}
	return nil
}

// Execute an if statement
func executeIfCmd(If *If) error {
	// Get condition value
	condVal, err := callIfFunc(ParseValue(If.Condition))
	if err != nil {
		return fmt.Errorf("%s: %s", If.Condition.Pos, err)
	}
	// Attempt to assert condition type as bool
	condBool, ok := condVal.(bool)
	if !ok {
		return errors.New("condition must be a boolean")
	}
	// If condition is true
	if condBool {
		// For each inner command
		for _, InnerCmd := range If.InnerCmds {
			// Execute command recursively
			err := executeCmd(InnerCmd)
			if err != nil {
				return fmt.Errorf("%s: %s", InnerCmd.Pos, err)
			}
		}
	}
	return nil
}

// Execute a repeat loop
func executeRptLoop(rptLoop *RptLoop) error {
	// Set loopRunning to true to allow break
	loopRunning = true
	// Run for loop with correct amount of iterations
rpt:
	for i := 0; i < *rptLoop.Times; i++ {
		// If user requested index variable via "{ var in ... }"
		if rptLoop.IndexVar != nil {
			// Set requested variable name to index
			Vars[*rptLoop.IndexVar] = i
		}
		// For each command within the loop
		for _, InnerCmd := range rptLoop.InnerCmds {
			// Execute command recursively
			err := executeCmd(InnerCmd)
			if err != nil {
				return fmt.Errorf("%s: %s", InnerCmd.Pos, err)
			}
			// If breakLoop set to true
			if breakLoop {
				// Reset breakLoop
				breakLoop = false
				break rpt
			}
		}
	}
	// Remove index variable if existent
	delete(Vars, *rptLoop.IndexVar)
	// Reset loopRunning
	loopRunning = false
	return nil
}

// Execute a while loop
func executeWhlLoop(whlLoop *WhlLoop) error {
	loopRunning = true
	// Get condition value
	condVal, err := callIfFunc(ParseValue(whlLoop.Condition))
	if err != nil {
		return fmt.Errorf("%s: %s", whlLoop.Condition.Pos, err)
	}
	// Attempt to assert condition type as bool
	condBool, ok := condVal.(bool)
	if !ok {
		return errors.New("condition must be a boolean")
	}
	// Run for loop if condition is true
whl:
	for condBool {
		// For each inner command
		for _, InnerCmd := range whlLoop.InnerCmds {
			// Execute command recursively
			err := executeCmd(InnerCmd)
			if err != nil {
				return fmt.Errorf("%s: %s", InnerCmd.Pos, err)
			}
			// If breakLoop set to true
			if breakLoop {
				// Reset breakLoop
				breakLoop = false
				break whl
			}
			// Get condition value
			condVal, err = callIfFunc(ParseValue(whlLoop.Condition))
			if err != nil {
				return fmt.Errorf("%s: %s", whlLoop.Condition.Pos, err)
			}
			// Attempt to assert condition type as bool and update its value
			condBool, ok = condVal.(bool)
			if !ok {
				return errors.New("condition must be a boolean")
			}
		}
	}
	loopRunning = false
	return nil
}

// Execute a function definition
func executeFuncDef(def *FuncDef) error {
	// Set requested function name in Funcs
	Funcs[*def.Name] = func(args map[string]interface{}) (interface{}, error) {
		funcRunning = true
		// Create new empty map[interface{}]interface{}
		argIMap := map[interface{}]interface{}{}
		// Convert args map[string]interface{} to map[interface{}]interface{}
		for key, value := range args {
			argIMap[key] = value
		}
		// Set variable _args to the args map[interface{}]interface{}
		Vars["_args"] = argIMap
		// For each command within the definition
		for _, InnerCmd := range def.InnerCmds {
			// Execute command recursively
			err := executeCmd(InnerCmd)
			if err != nil {
				return nil, fmt.Errorf("%s: %s", InnerCmd.Pos, err)
			}
			if retValue != nil {
				ret := retValue
				retValue = nil
				funcRunning = false
				return ret, nil
			}
		}
		// Remove args variable from Vars
		delete(Vars, "_args")
		funcRunning = false
		return nil, nil
	}
	return nil
}

// Parse and execute command
func executeCmd(cmd *Command) error {
	// If parsing variables
	if cmd.Vars != nil {
		// For each variable
		for _, Var := range cmd.Vars {
			// Attempt to execute the variable command
			err := executeVarCmd(Var)
			if err != nil {
				return err
			}
		}
	} else if cmd.Calls != nil {
		// For each function call
		for _, Call := range cmd.Calls {
			// Attempt to call function
			_, err := CallFunction(Call)
			if err != nil {
				return fmt.Errorf("%s: %s", Call.Pos, err)
			}
		}
	} else if cmd.Ifs != nil {
		// For each if statement
		for _, If := range cmd.Ifs {
			// Attempt to execute the if command
			err := executeIfCmd(If)
			if err != nil {
				return err
			}
		}
	} else if cmd.RptLoops != nil {
		// For each repeat loop
		for _, RptLoop := range cmd.RptLoops {
			// Attempt to execute the repeat loop
			err := executeRptLoop(RptLoop)
			if err != nil {
				return err
			}
		}
	} else if cmd.WhlLoops != nil {
		// For each while loop
		for _, WhlLoop := range cmd.WhlLoops {
			// Attempt to execute the while loop
			err := executeWhlLoop(WhlLoop)
			if err != nil {
				return err
			}
		}
	} else if cmd.Defs != nil {
		// For each function definition
		for _, Def := range cmd.Defs {
			// Attempt to execute the function definition
			err := executeFuncDef(Def)
			if err != nil {
				return err
			}
		}
	}
	return nil
}

// Command stores any commands encountered while parsing a script
type Command struct {
	Pos      lexer.Position
	Vars     []*Var      `( @@`
	Ifs      []*If       `| @@`
	RptLoops []*RptLoop  `| @@`
	WhlLoops []*WhlLoop  `| @@`
	Defs     []*FuncDef  `| @@`
	Calls    []*FuncCall `| @@)`
}

// Value stores any literal values encountered while parsing a script
type Value struct {
	Pos    lexer.Position
	String *string      `  @String`
	Number *float64     `| @Number`
	Bool   *Bool        `| @("true" | "false")`
	SubCmd *FuncCall    `| "(" @@ ")"`
	VarVal *VarVal      `| @@`
	Expr   *Expression  `| "{" @@ "}"`
	Map    []*MapKVPair `| "[" (@@ ("," @@)* )? "]"`
	Array  []*Value     `| "[" (@@ ("," @@)* )? "]"`
	Opposite *Value `| "!" @@`
}

// Bool stores boolean values encountered while parsing a script.
// It is required for the Capture method
type Bool bool

// Capture parses a boolean literal encountered in the script into
// a Go boolean value
func (b *Bool) Capture(values []string) error {
	// Convert string to boolean
	*b = values[0] == "true"
	return nil
}

// FuncCall stores any function calls encountered while parsing a script
type FuncCall struct {
	Pos  lexer.Position
	Name string `@Ident @("-" Ident)*`
	Args []*Arg `@@*`
}

// Arg stores arguments for function calls
type Arg struct {
	Pos   lexer.Position
	Key   string `("with" @Ident)?`
	Value *Value `@@`
}

// VarVal stores any references to a variable encountered while parsing a script
type VarVal struct {
	Name  *string `"$" @Ident`
	Index *Value  `("[" @@ "]")?`
}

// Expression stores any expressions encountered while parsing a
// script for later evaluation
type Expression struct {
	Pos       lexer.Position
	Left      *Value          `@@`
	RightSegs []*ExprRightSeg `@@*`
}

// ExprRightSeg stores segments of the right side of an expression
type ExprRightSeg struct {
	Op    string `@Operator`
	Right *Value `@@`
}

// MapKVPair stores any key/value pairs encountered while parsing map literals
type MapKVPair struct {
	Key   *Value `@@`
	Value *Value `":" @@`
}

// FuncDef stores any function definitions encountered while parsing a script
type FuncDef struct {
	Pos       lexer.Position
	Name      *string    `"define" @Ident "{"`
	InnerCmds []*Command `@@* "}"`
}

// Var stores any variables encountered while parsing a script
type Var struct {
	Pos   lexer.Position
	Key   string `"set" @Ident`
	Index *Value `("[" @@ "]")?`
	Value *Value `"to" @@`
}

// If stores any if statements encountered while parsing a script
type If struct {
	Pos       lexer.Position
	Condition *Value     `"if" @@ "{"`
	InnerCmds []*Command `@@* "}"`
}

// RptLoop stores any repeat loops encountered while parsing a script
type RptLoop struct {
	Pos       lexer.Position
	Times     *int       `"repeat" @Number "times" "{"`
	IndexVar  *string    `(@Ident "in")?`
	InnerCmds []*Command `@@* "}"`
}

// WhlLoop stores any while loops encountered while parsing a script
type WhlLoop struct {
	Pos       lexer.Position
	Condition *Value     `"loop" "while" @@ "{"`
	InnerCmds []*Command `@@* "}"`
}