dynamo-browse/internal/dynamo-browse/models/queryexpr/placeholder.go

package queryexpr

import (
	"github.com/lmika/dynamo-browse/internal/dynamo-browse/models"
	"github.com/pkg/errors"
)

const (
	valuePlaceholderPrefix = '$'
	namePlaceholderPrefix  = ':'
)

func (p *astPlaceholder) evalToIR(ctx *evalContext, info *models.TableInfo) (irAtom, error) {
	placeholderType := p.Placeholder[0]
	placeholder := p.Placeholder[1:]

	if placeholderType == valuePlaceholderPrefix {
		val, hasVal := ctx.lookupValue(placeholder)
		if !hasVal {
			return nil, MissingPlaceholderError{Placeholder: p.Placeholder}
		}

		ev, err := newExprValueFromAttributeValue(val)
		if err != nil {
			return nil, err
		}

		return irValue{value: ev}, nil
	} else if placeholderType == namePlaceholderPrefix {
		name, hasName := ctx.lookupName(placeholder)
		if !hasName {
			return nil, MissingPlaceholderError{Placeholder: p.Placeholder}
		}

		return irNamePath{name, nil}, nil
	}

	return nil, errors.New("unrecognised placeholder")
}

func (p *astPlaceholder) evalItem(ctx *evalContext, item models.Item) (exprValue, error) {
	placeholderType := p.Placeholder[0]
	placeholder := p.Placeholder[1:]

	if placeholderType == valuePlaceholderPrefix {
		val, hasVal := ctx.lookupValue(placeholder)
		if !hasVal {
			return nil, MissingPlaceholderError{Placeholder: p.Placeholder}
		}
		return newExprValueFromAttributeValue(val)
	} else if placeholderType == namePlaceholderPrefix {
		name, hasName := ctx.lookupName(placeholder)
		if !hasName {
			return nil, MissingPlaceholderError{Placeholder: p.Placeholder}
		}

		res, hasV := item[name]
		if !hasV {
			return nil, nil
		}

		return newExprValueFromAttributeValue(res)
	}

	return nil, errors.New("unrecognised placeholder")
}

func (p *astPlaceholder) canModifyItem(ctx *evalContext, item models.Item) bool {
	placeholderType := p.Placeholder[0]
	return placeholderType == namePlaceholderPrefix
}

func (p *astPlaceholder) setEvalItem(ctx *evalContext, item models.Item, value exprValue) error {
	placeholderType := p.Placeholder[0]
	placeholder := p.Placeholder[1:]

	if placeholderType == valuePlaceholderPrefix {
		return PathNotSettableError{}
	} else if placeholderType == namePlaceholderPrefix {
		name, hasName := ctx.lookupName(placeholder)
		if !hasName {
			return MissingPlaceholderError{Placeholder: p.Placeholder}
		}

		item[name] = value.asAttributeValue()
		return nil
	}

	return errors.New("unrecognised placeholder")
}

func (p *astPlaceholder) deleteAttribute(ctx *evalContext, item models.Item) error {
	placeholderType := p.Placeholder[0]
	placeholder := p.Placeholder[1:]

	if placeholderType == valuePlaceholderPrefix {
		return PathNotSettableError{}
	} else if placeholderType == namePlaceholderPrefix {
		name, hasName := ctx.lookupName(placeholder)
		if !hasName {
			return MissingPlaceholderError{Placeholder: p.Placeholder}
		}

		delete(item, name)
		return nil
	}

	return errors.New("unrecognised placeholder")
}

func (p *astPlaceholder) String() string {
	return p.Placeholder
}