package salix import ( "errors" "go.elara.ws/salix/internal/ast" ) var ( ErrIfExpectsOneArg = errors.New("if tag expects one argument") ErrIfExpectsBool = errors.New("if tag expects a bool value") ErrIfTwoElse = errors.New("if tags can only have one else tag inside") ) // ifTag represents a #if tag within a Salix template type ifTag struct{} func (it ifTag) Run(tc *TagContext, block, args []ast.Node) error { if len(args) != 1 { return ErrIfExpectsOneArg } inner, err := it.findInner(block) if err != nil { return err } val, err := tc.GetValue(args[0], nil) if err != nil { return err } cond, ok := val.(bool) if !ok { return ErrIfExpectsBool } if cond { return tc.Execute(block[:inner.endRoot], nil) } else { if len(inner.elifTags) > 0 { for i, elifTag := range inner.elifTags { val, err := tc.GetValue(elifTag.value, nil) if err != nil { return err } cond, ok := val.(bool) if !ok { return ErrIfExpectsBool } nextIndex := len(block) if i < len(inner.elifTags)-1 { nextIndex = inner.elifTags[i+1].index } else if inner.elseIndex != 0 { nextIndex = inner.elseIndex } if cond { return tc.Execute(block[elifTag.index+1:nextIndex], nil) } } } if inner.elseIndex != 0 { return tc.Execute(block[inner.elseIndex+1:], nil) } } return nil } type innerTags struct { endRoot int elifTags []elif elseIndex int } type elif struct { index int value ast.Node } // findInner finds the inner elif and else tags in a block // passed to the if tag. func (it ifTag) findInner(block []ast.Node) (innerTags, error) { var out innerTags for i, node := range block { if tag, ok := node.(ast.Tag); ok { switch tag.Name.Value { case "elif": if out.endRoot == 0 { out.endRoot = i } if len(tag.Params) > 1 { return innerTags{}, ErrIfExpectsOneArg } out.elifTags = append(out.elifTags, elif{ index: i, value: tag.Params[0], }) case "else": if out.elseIndex != 0 { return innerTags{}, ErrIfTwoElse } if out.endRoot == 0 { out.endRoot = i } out.elseIndex = i break } } } if out.endRoot == 0 { out.endRoot = len(block) } return out, nil }