yacc.y

%{

package main

import (
  "fmt"
  "strconv"
  "strings"
  "os"
  "mhoc.co/msp/ast"
  "mhoc.co/msp/log"
)

// Each of the node types is stored in our %union
// The return types of each grammar rule is written in a comment above the rule
// If we know the type, we use a specific element in this struct so as to
// cut down on type inferencing
// If we dont know the type (aka: statement), then we just use the "No" element

%}

%union {
  N ast.Node
  Str string
}

%token
  ASSERT
  RETURN
  FUNCTION
	SCRIPT_TAG_START
	SCRIPT_TAG_END
	VARDEF
	IDENTIFIER
  OBJKEY
	DOCUMENT_WRITE
	NEWLINE
	WHITESPACE
	SEMICOLON
  TRUE FALSE
  IF ELSE
  DO WHILE
  BREAK CONTINUE
  LPAREN RPAREN
  LBRACKET RBRACKET
  LBRACE RBRACE
  EQUAL
	INTEGER
	PLUS
	MINUS
	MULT
	DIVIDE
	STRING
	COMMA
	COLON
  GT
  LT
  GTE
  LTE
  EQUIV
  NEQUIV
  AND
  OR
  NOT

%%

target:
  file {
    log.Trace("grm", "Target")
    fmt.Print("")
    $1.N.Execute()
  }
;

// File -> StatementList
// Beginning and end script tags with a program in-between them
file:
	SCRIPT_TAG_START newlines program SCRIPT_TAG_END {
    log.Trace("grm", "File: start,newlines,program,end")
    $$.N = $3.N
  }
	| SCRIPT_TAG_START newlines program SCRIPT_TAG_END newlines {
    log.Trace("grm", "File: start,newlines,program,end,newlines")
    $$.N = $3.N
  }
	| newlines SCRIPT_TAG_START newlines program SCRIPT_TAG_END newlines {
    log.Trace("grm", "File: newlines,start,newlines,program,end,newlines")
    $$.N = $4.N
  }
;

// Program -> StatementList
// A list of statement lines each separated by a newlines
program:
	program line {
    log.Trace("grm", "Program: Appending program line")
    line_statements := $2.N.(*ast.StatementList).List
    for _, item := range line_statements {
      $1.N.(*ast.StatementList).List = append($1.N.(*ast.StatementList).List, item)
    }
    $$.N = $1.N
  } newlines
  | {
    log.Trace("grm", "Program: Creating new statement list")
    $$.N = &ast.StatementList{Line: log.LineNo, List: make([]*ast.Statement, 0, 0)}
  }
;

// Line -> StatementList
// A single line in the program. A line can contain multiple statements through
// the use of a semicolon
line:
  recursive_line
  | if_statement {
    $$.N = &ast.StatementList{Line: log.LineNo, List: []*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}}
  }
  | while_statement {
    $$.N = &ast.StatementList{Line: log.LineNo, List: []*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}}
  }
  | do_while_statement {
    $$.N = &ast.StatementList{Line: log.LineNo, List: []*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}}
  }
  | function_definition {
    $$.N = &ast.StatementList{Line: log.LineNo, List: []*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}}
  }
;

// RecursiveLine -> StatementList
// This is necessary to require if and loop statmenets to have their own line
recursive_line:
	statement {
    log.Trace("grm", "Line: Creating a new single statement statementlist")
    $$.N = &ast.StatementList{Line: log.LineNo, List: []*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}}
  }
	| statement SEMICOLON {
    log.Trace("grm", "Line Creating a new single statement statementlist;")
    $$.N = &ast.StatementList{Line: log.LineNo, List: []*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}}
  }
	| statement SEMICOLON recursive_line {
    // Prepend this statement to the list already created above
    // Because of the weird way the recursion is set up here, we have to prepend instead of append
    // This is the idiomatic way to prepend in go. Looks weird. It works.
    $3.N.(*ast.StatementList).List = append([]*ast.Statement{&ast.Statement{N:$1.N, Line: log.LineNo}}, $3.N.(*ast.StatementList).List...)
    $$.N = $3.N
  }
;

// Statement -> Node
// Any single statement in the program. Statements have no value in this language.
statement:
	declaration
	| assignment
	| definition
  | function_call
  | BREAK
  | CONTINUE
  | RETURN expression {
    $$.N = &ast.Return{Line: log.LineNo, Value: $2.N}
  }
  | ASSERT LPAREN expression RPAREN {
    $$.N = &ast.Assert{Line: log.LineNo, Value: $3.N}
  }
	| DOCUMENT_WRITE LPAREN parameter_list RPAREN {
    $3.N.(*ast.FunctionCall).Name = "document.write"
    $$.N = $3.N
  }
;

// Declaration -> Declaration
// The declaration or redeclaration of a variable
declaration:
	VARDEF IDENTIFIER {
    $$.N = &ast.Declaration{Line: log.LineNo, Name: $2.Str}
  }
;

// Assignment -> Assignment
// The assignment of a value to a variable which has already been declared
assignment:
	IDENTIFIER EQUAL value {
    log.Trace("grm", "Assignment Identifier")
    $$.N = &ast.Assignment{Line: log.LineNo, Type: ast.VAR_NORM, Name: $1.Str, Rhs: $3.N}
  }
  | OBJKEY EQUAL value {
    log.Trace("grm", "Assignment Obj Key")
    sp := strings.Split($1.Str, ".")
    $$.N = &ast.Assignment{Line: log.LineNo, Type: ast.VAR_OBJECT, Name: sp[0], ObjChild: sp[1], Rhs: $3.N}
  }
  | IDENTIFIER LBRACKET expression RBRACKET EQUAL value {
    log.Trace("grm", "Assignment to Array Index")
    $$.N = &ast.Assignment{Line: log.LineNo, Type: ast.VAR_ARRAY, Name: $1.Str, Index: $3.N, Rhs: $6.N}
  }
;

// Definition -> Definition
// A combination declaration and assignment
definition:
	VARDEF IDENTIFIER EQUAL value {
    // Create the declaration
    decl := &ast.Declaration{Name: $2.Str, Line: log.LineNo}
    // Create the assignment
    assign := &ast.Assignment{Name: $2.Str, Rhs: $4.N, Line: log.LineNo}
    // Combine them into a definition
    def := &ast.Definition{Decl: decl, Assign: assign, Line: log.LineNo}
    $$.N = def
  }
;

// Parameter List -> FunctionCall
// The list of parameters which a function is called.
// This is where we build the actual function call that gets added to the ast
parameter_list:
	expression {
    // Create a new function call with a single argument
    fc := &ast.FunctionCall{Line: log.LineNo, Args: []ast.Statement{ast.Statement{N:$1.N, Line: log.LineNo}}}
    $$.N = fc
  }
	| parameter_list COMMA expression {
    // Append this expression to our list of arguments from $1
    $1.N.(*ast.FunctionCall).Args = append($1.N.(*ast.FunctionCall).Args, ast.Statement{N:$3.N, Line: log.LineNo})
    $$.N = $1.N
  }
	| {
    // Create an empty argument function call
    $$.N = &ast.FunctionCall{Line: log.LineNo, Args: []ast.Statement{}}
  }
;

// Value -> Node
// Anything in the language which can be assigned to a variable
value:
	expression
	| object_definition
  | array_definition
;

// Expression -> Node
// Any combination of multiple sub-expressions to produce a single value
expression:
	boolean_expression
  | NOT expression {
    $$.N = &ast.UnaryExpression{Line: log.LineNo, Value: $2.N, Op: "!"}
  }
;

// Boolean Expression -> Node
// Order of operations level 5
boolean_expression:
  relational_expression
  | boolean_expression AND relational_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "&&"}
  }
  | boolean_expression OR relational_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "||"}
  }
;

// Relational Expression -> Node
// Order of operations level 4
relational_expression:
  additive_expression
  | relational_expression GT additive_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: ">"}
  }
  | relational_expression LT additive_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "<"}
  }
  | relational_expression LTE additive_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "<="}
  }
  | relational_expression GTE additive_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: ">="}
  }
  | relational_expression EQUIV additive_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "=="}
  }
  | relational_expression NEQUIV additive_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "!="}
  }
;

// Additive Expression -> Node
// Order of operations level 3
additive_expression:
	multiplicative_expression
	| additive_expression PLUS multiplicative_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "+"}
  }
	| additive_expression MINUS multiplicative_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "-"}
  }
;

// Multiplicative Expression -> Node
// Order of operations level 2
multiplicative_expression:
	primary_expression
	| multiplicative_expression MULT primary_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "*"}
  }
	| multiplicative_expression DIVIDE primary_expression {
    $$.N = &ast.BinaryExpression{Line: log.LineNo, Lhs: $1.N, Rhs: $3.N, Op: "/"}
  }
;

// Primary Expression -> Node
// Order of operations level 1
primary_expression:
	INTEGER
	| STRING
  | TRUE
  | FALSE
	| variable_reference
  | IDENTIFIER LPAREN parameter_list RPAREN {
    $3.N.(*ast.FunctionCall).Name = $1.Str
    $$.N = $3.N
  }
	| LPAREN expression RPAREN {
    $$.N = $2.N
  }
;

// Variable Reference -> Reference
// Any usage of a variable inside a value
variable_reference:
	IDENTIFIER {
    // Create the reference object
    // We dont actually look up and store the value of the variable until execution
    $$.N = &ast.Reference{Line: log.LineNo, Type: ast.VAR_NORM, Name: $1.Str}
  }
  | OBJKEY {
    sp := strings.Split($1.Str, ".")
    $$.N = &ast.Reference{Line: log.LineNo, Type: ast.VAR_OBJECT, Name: sp[0], ObjChild: sp[1]}
  }
  | IDENTIFIER LBRACKET expression RBRACKET {
    $$.N = &ast.Reference{Line: log.LineNo, Type: ast.VAR_ARRAY, Name: $1.Str, Index: $3.N}
  }
;

// Object definition -> Object
// The typed definition of an object inside the source code
object_definition:
	LBRACE field_list RBRACE {
    $$.N = $2.N
  }
	| LBRACE newlines field_list RBRACE {
    $$.N = $3.N
  }
;

// Field List -> Object
// The list of fields without the braces around them
field_list:
	interim_field_list final_field {
    // Add the final field to the list of all the fields
    $1.N.(*ast.Object).Map[$2.N.(*ast.Field).FieldName] = $2.N.(*ast.Field).FieldValue
    $$.N = $1.N
  }
	| {
    // Return an empty object
    $$.N = &ast.Object{Line: log.LineNo, Map: make(map[string]ast.Node)}
  }
;

// Interim Field List -> Object
// This is every field in the object definition except for the last one
// due to the fact that the last one is the only one without a comma after it
interim_field_list:
	interim_field_list interim_field {
    // Add the interim field to the list of all interim fields
    $1.N.(*ast.Object).Map[$2.N.(*ast.Field).FieldName] = $2.N.(*ast.Field).FieldValue
    $$.N = $1.N
  }
	| {
    // Return an empty list of interim fields
    $$.N = &ast.Object{Line: log.LineNo, Map: make(map[string]ast.Node)}
  }
;

// Interim field -> Field
// A single field followed by a required comma
interim_field:
	field COMMA
	| field COMMA newlines
;

// Final field -> Field
// A single field followed by no comma
final_field:
	field
	| field newlines
;

// Field -> Field
// A single key:value pair
field:
	IDENTIFIER COLON expression {
    $$.N = &ast.Field{Line: log.LineNo, FieldName: $1.Str, FieldValue: $3.N}
  }
;

// If statement -> ast.If
if_statement:
  IF LPAREN expression RPAREN LBRACE newlines program RBRACE if_tail {
    // Create a branch for this if statement
    fBranch := &ast.Branch{Conditional: $3.N, IfTrue: $7.N.(*ast.StatementList), Line: $3.N.LineNo()}

    // Prepend this if statement to the list of if statements in iftail
    iff := $9.N.(*ast.If)
    iff.Branches = append([]*ast.Branch{fBranch}, iff.Branches...)
    $$.N = iff
  }

;

// If tail -> ast.If
if_tail:
  ELSE if_statement {
    // Pass up the if statement created in $2
    $$.N = $2.N
  }
  | ELSE LBRACE newlines program RBRACE {
    // Create the if statement with an else
    $$.N = &ast.If{Branches: make([]*ast.Branch, 0, 0), HasElse: true, Else: $4.N.(*ast.StatementList), Line: log.LineNo}
  }
  | {
    // Create the if statement with no else
    $$.N = &ast.If{Branches: make([]*ast.Branch, 0, 0), HasElse: false, Line: log.LineNo}
  }
;

// Arrays -> Object
// Under the hood, arrays are literally just objects. I dont even have a separate
// type in the ast for them because there doesnt appear to be any need. Once
// they are evaluated at runtime I convert it into an ast.Value with type=VALUE_ARRAY,
// but even then the ast.Value.Value interface is exactly the same as an object.
array_definition:
  LBRACKET array_list RBRACKET {
    $$.N = $2.N
    log.ArrayIndexNo = 0
  }
  | LBRACKET newlines array_list RBRACKET {
    $$.N = $3.N
    log.ArrayIndexNo = 0
  }
;

// Array List -> Object
array_list:
	interim_array_list final_array_item {
    // Add the final array item to the list of all items
    $1.N.(*ast.Array).Map[$2.N.(*ast.Field).FieldName] = $2.N.(*ast.Field).FieldValue
    $$.N = $1.N
  }
	| {
    // Return an empty object
    $$.N = &ast.Array{Line: log.LineNo, Map: make(map[string]ast.Node)}
  }
;

// Interim Array List -> Object
// Literally look up at the object code. Its exactly the same. EXACTLY.
interim_array_list:
	interim_array_list interim_array_item {
    // Add the interim array item to the list of all iterim array items
    $1.N.(*ast.Array).Map[$2.N.(*ast.Field).FieldName] = $2.N.(*ast.Field).FieldValue
    $$.N = $1.N
  }
	| {
    // Return an empty list of interim array items
    $$.N = &ast.Array{Line: log.LineNo, Map: make(map[string]ast.Node)}
  }
;

// Interim array item -> Field
// The field name is the index of the array. This is determined by a global
// integer stored in the log package
interim_array_item:
	array_item COMMA
	| array_item COMMA newlines
;

// Final array item -> Field
final_array_item:
	array_item
	| array_item newlines
;

// A single array item -> Field
array_item:
  expression {
    // Create the field
    f := &ast.Field{Line: log.LineNo, FieldName: strconv.Itoa(log.ArrayIndexNo), FieldValue: $1.N}
    log.ArrayIndexNo++
    $$.N = f
  }
;

// While statement -> Loop
while_statement:
  WHILE LPAREN expression RPAREN LBRACE newlines program RBRACE {
    $$.N = &ast.Loop{Line: $3.N.LineNo(), Conditional: $3.N, Body: $7.N.(*ast.StatementList), PreCheck: true}
  }
;

// Do-While -> Loop
do_while_statement:
  DO LBRACE newlines program RBRACE newline WHILE LPAREN expression RPAREN {
    $$.N = &ast.Loop{Line: $9.N.LineNo(), Conditional: $9.N, Body: $4.N.(*ast.StatementList), PreCheck: false}
  }
  | DO LBRACE newlines program RBRACE newline WHILE LPAREN expression RPAREN SEMICOLON {
    $$.N = &ast.Loop{Line: $9.N.LineNo(), Conditional: $9.N, Body: $4.N.(*ast.StatementList), PreCheck: false}
  }
;

// Function definition -> FunctionDef
function_definition:
  FUNCTION IDENTIFIER LPAREN parameter_list RPAREN LBRACE newlines program RBRACE {
    // Get the list of argument names
    // the Parameter_list thinks that each item is actually a variable reference (hacky lol)
    varStatementList := $4.N.(*ast.FunctionCall).Args
    varNames := []string{}
    for _, varStatement := range varStatementList {
      switch varStatement.N.(type) {
        case *ast.Reference:
          varNames = append(varNames, varStatement.N.(*ast.Reference).Name)
        default:
          fmt.Fprintf(os.Stderr, "syntax error\n")
          os.Exit(1)
      }
    }
    $$.N = &ast.FunctionDef{Line: $4.N.LineNo(), Name: $2.Str, ArgNames: varNames, ExecMiniscript:true, MSBody:*$8.N.(*ast.StatementList)}
  }
;

// Function call -> FunctionCall
function_call:
  IDENTIFIER LPAREN parameter_list RPAREN {
    $3.N.(*ast.FunctionCall).Name = $1.Str
    $$.N = $3.N
  }
;

// New Lines -> Nothing
// This is so weird and I hate it but it works
// Previously I had '\n+' as NEWLINE in my lexer, but I wanted to be able to maintain
// my own linenumber count so I changed it to '\n'. Then everything stopped
// working if the user had more than 1 newline. So this is an emulation of
// the \n+ behavior. Oh yes.
newline:
  NEWLINE {
    log.LineNo++
  }
;

newlines:
  NEWLINE {
    log.LineNo++
  }
  | newlines NEWLINE {
    log.LineNo++
  }
;

%%