salix/parser/salix.peg

/*
 * Salix - Go templating engine
 * Copyright (C) 2023 Elara Musayelyan
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

{
package parser

import (
    "strconv"

    "go.elara.ws/salix/ast"
)

func toAnySlice(v any) []any {
    if v == nil {
        return nil
    }
    return v.([]any)
}

func toNodeSlice(v any) []ast.Node {
    if v == nil {
        return nil
    }
    return v.([]ast.Node)
}

func getPos(c *current) ast.Position {
    return ast.Position{
        Line: c.pos.line,
        Col:  c.pos.col,
    }
}

func toExpr(c *current, first, rest any) ast.Node {
    restSlice := toAnySlice(rest)
    if len(restSlice) == 0 {
        return first.(ast.Node)
    }
    
    out := ast.Expr{First: first.(ast.Node), Position: getPos(c)}
    for _, restValue := range restSlice {
        valueSlice := toAnySlice(restValue)
        out.Rest = append(out.Rest, ast.Expr{
            Operator: valueSlice[1].(ast.Operator),
            First:  valueSlice[3].(ast.Node),
            Position: valueSlice[3].(ast.Node).Pos(),
        })
    }
    
    return out
}

}

Root = items:(Tag / ExprTag / EndTag / Text)* {
    itemSlice := toAnySlice(items)
    out := make([]ast.Node, len(itemSlice))
    for i, item := range itemSlice{
        out[i] = item.(ast.Node)
    }
    return out, nil
}

Tag = '#' name:Ident params:ParamList? body:':'? {
    return ast.Tag{
        Name:     name.(ast.Ident),
        Params:   toNodeSlice(params),
        HasBody:  body != nil,
        Position: getPos(c),
    }, nil
}

EndTag = "#!" name:Ident {
    return ast.EndTag{
        Name:     name.(ast.Ident),
        Position: getPos(c),
    }, nil
}

ExprTag = "#(" item:Expr ')' {
    return ast.ExprTag{
        Value:    item.(ast.Node),
        Position: getPos(c),
    }, nil
}

Expr = Ternary / Assignment / LogicalExpr
Assignable = Ternary / LogicalExpr

LogicalExpr = _ first:ComparisonExpr rest:(_ LogicalOp _ ComparisonExpr)* _ {
    return toExpr(c, first, rest), nil
}

ComparisonExpr = _ first:ArithmeticExpr rest:(_ ComparisonOp _ ArithmeticExpr)* _ {
    return toExpr(c, first, rest), nil
}

ArithmeticExpr = _ first:Value rest:(_ ArithmeticOp _ Value)* _ {
    return toExpr(c, first, rest), nil
}

ParenExpr = '(' expr:Expr ')' {
    return expr, nil
}

ParamList = '(' params:(Expr ( ',' _ Expr )* )? ')' {
    paramSlice := toAnySlice(params)
    if len(paramSlice) == 0 {
        return []ast.Node{}, nil
    }
    out := []ast.Node{paramSlice[0].(ast.Node)}
    restSlice := toAnySlice(paramSlice[1])
    for _, value := range restSlice {
        valueSlice := toAnySlice(value)
        out = append(out, valueSlice[2].(ast.Node))
    }
    return out, nil
}

Value = not:"!"? node:(MethodCall / FieldAccess / Index / String / RawString / Float / Integer / Bool / FuncCall / VariableOr / Ident / ParenExpr) {
    return ast.Value{
        Node: node.(ast.Node),
        Not:  not != nil,
    }, nil
}

VariableOr = variable:Ident _ '|' _ or:Assignable {
    return ast.VariableOr{
        Variable: variable.(ast.Ident),
        Or:       or.(ast.Node),
    }, nil
}

Assignment = name:Ident _ '=' _ value:Assignable {
    return ast.Assignment{
        Name:     name.(ast.Ident),
        Value:    value.(ast.Node),
        Position: getPos(c),
    }, nil
}

Ternary = cond:Assignable _ '?' _ ifTrue:Value _ ':' _ elseVal:Value {
    return ast.Ternary{
        Condition: cond.(ast.Node),
        IfTrue:    ifTrue.(ast.Node),
        Else:      elseVal.(ast.Node),
    }, nil
}

MethodCall = value:Value '.' name:Ident params:ParamList {
    return ast.MethodCall{
        Value:    value.(ast.Node),
        Name:     name.(ast.Ident),
        Params:   toNodeSlice(params),
        Position: getPos(c),
    }, nil
}

Index = value:Value '[' index:Value ']' {
    return ast.Index{
        Value:    value.(ast.Node),
        Index:    index.(ast.Node),
        Position: getPos(c),
    }, nil
}

FieldAccess = value:Value '.' name:Ident {
    return ast.FieldAccess{
        Value:    value.(ast.Node),
        Name:     name.(ast.Ident),
        Position: getPos(c),
    }, nil
}

Ident = [a-z]i [a-z0-9_]i* { 
    return ast.Ident{
        Value:    string(c.text),
        Position: getPos(c),
    }, nil
}

FuncCall = name:Ident params:ParamList {
    return ast.FuncCall{
        Name:     name.(ast.Ident),
        Params:   toNodeSlice(params),
        Position: getPos(c),
    }, nil
}

Integer = '-'? ("0x" [0-9a-f]i+ / "0o" [0-7]+ / "0b" [01]+ / [0-9]+) {
    i, err := strconv.ParseInt(string(c.text), 0, 64)
    return ast.Integer{
        Value:    i,
        Position: getPos(c),
    }, err
}

Float = '-'? value:([0-9]+ '.' [0-9]+) {
    f, err := strconv.ParseFloat(string(c.text), 64)
    return ast.Float{
        Value:    f,
        Position: getPos(c),
    }, err
}

String = '"' value:[^"]* '"' {
    s, err := strconv.Unquote(string(c.text))
    return ast.String{
        Value:    s,
        Position: getPos(c),
    }, err
}

RawString = '`' value:[^`]* '`' {
    s, err := strconv.Unquote(string(c.text))
    return ast.String{
        Value:    s,
        Position: getPos(c),
    }, err
}

Bool = ("true"i / "false"i) {
    b, err := strconv.ParseBool(string(c.text))
    return ast.Bool{
        Value:    b,
        Position: getPos(c),
    }, err
}

LogicalOp = ("||" / "&&") {
    return ast.Operator{
        Value:    string(c.text),
        Position: getPos(c),
    }, nil
}

ComparisonOp = ("==" / "<=" / ">=" / '<' / '>' / "in"i) {
    return ast.Operator{
        Value:    string(c.text),
        Position: getPos(c),
    }, nil
}

ArithmeticOp = ('+' / '-' / '/' / '*' / '%') {
    return ast.Operator{
        Value:    string(c.text),
        Position: getPos(c),
    }, nil
}

Text = . [^#]* { return ast.Text{Data: c.text, Position: getPos(c)}, nil }

_ "whitespace" ← [ \t\r\n]*