// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module parser

import v.ast

fn (mut p Parser) assign_stmt() ast.Stmt {
	return p.partial_assign_stmt(p.expr_list())
}

fn (mut p Parser) check_undefined_variables(exprs []ast.Expr, val ast.Expr) {
	match val {
		ast.Ident {
			for expr in exprs {
				if expr is ast.Ident {
					ident := expr as ast.Ident
					if ident.name == val.name {
						p.error_with_pos('undefined variable: `$val.name`', val.pos)
					}
				}
			}
		}
		ast.InfixExpr {
			p.check_undefined_variables(exprs, val.left)
			p.check_undefined_variables(exprs, val.right)
		}
		ast.ParExpr {
			p.check_undefined_variables(exprs, val.expr)
		}
		ast.PostfixExpr {
			p.check_undefined_variables(exprs, val.expr)
		}
		ast.PrefixExpr {
			p.check_undefined_variables(exprs, val.right)
		}
		ast.StringInterLiteral {
			for expr_ in val.exprs {
				p.check_undefined_variables(exprs, expr_)
			}
		}
		else {}
	}
}

fn (mut p Parser) check_cross_variables(exprs []ast.Expr, val ast.Expr) bool {
	match val {
		ast.Ident { for expr in exprs {
				if expr is ast.Ident {
					ident := expr as ast.Ident
					if ident.name == val.name {
						return true
					}
				}
			} }
		ast.InfixExpr { return p.check_cross_variables(exprs, val.left) || p.check_cross_variables(exprs, val.right) }
		ast.PrefixExpr { return p.check_cross_variables(exprs, val.right) }
		ast.PostfixExpr { return p.check_cross_variables(exprs, val.expr) }
		else {}
	}
	return false
}

fn (mut p Parser) partial_assign_stmt(left []ast.Expr) ast.Stmt {
	p.is_stmt_ident = false
	op := p.tok.kind
	pos := p.tok.position()
	p.next()
	right := p.expr_list()
	mut has_cross_var := false
	if op == .decl_assign {
		// a, b := a + 1, b
		for r in right {
			p.check_undefined_variables(left, r)
		}
	} else if left.len > 1 {
		// a, b = b, a
		for r in right {
			has_cross_var = p.check_cross_variables(left, r)
		}
	}
	for i, lx in left {
		match lx {
			ast.Ident {
				if op == .decl_assign {
					if p.scope.known_var(lx.name) {
						p.error_with_pos('redefinition of `$lx.name`', lx.pos)
					}
					if left.len == right.len {
						p.scope.register(lx.name, ast.Var{
							name: lx.name
							expr: right[i]
							is_mut: lx.is_mut || p.inside_for
							pos: lx.pos
						})
					} else {
						p.scope.register(lx.name, ast.Var{
							name: lx.name
							is_mut: lx.is_mut || p.inside_for
							pos: lx.pos
						})
					}
				}
			}
			ast.IndexExpr {
				if op == .decl_assign {
					p.error_with_pos('non-name `$lx.left[$lx.index]` on left side of `:=`',
						lx.pos)
				}
				lx.is_setter = true
			}
			ast.ParExpr {}
			ast.PrefixExpr {}
			ast.SelectorExpr {
				if op == .decl_assign {
					p.error_with_pos('struct fields can only be declared during the initialization',
						lx.pos)
				}
			}
			else {
				// TODO: parexpr ( check vars)
				// else { p.error_with_pos('unexpected `${typeof(lx)}`', lx.position()) }
			}
		}
	}
	return ast.AssignStmt{
		op: op
		left: left
		right: right
		pos: pos
		has_cross_var: has_cross_var
		is_simple: p.inside_for && p.tok.kind == .lcbr
	}
}