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package query
import (
"time"
"github.com/pelletier/go-toml"
)
// NodeFilterFn represents a user-defined filter function, for use with
// Query.SetFilter().
//
// The return value of the function must indicate if 'node' is to be included
// at this stage of the TOML path. Returning true will include the node, and
// returning false will exclude it.
//
// NOTE: Care should be taken to write script callbacks such that they are safe
// to use from multiple goroutines.
type NodeFilterFn func(node interface{}) bool
// Result is the result of Executing a Query.
type Result struct {
items []interface{}
positions []toml.Position
}
// appends a value/position pair to the result set.
func (r *Result) appendResult(node interface{}, pos toml.Position) {
r.items = append(r.items, node)
r.positions = append(r.positions, pos)
}
// Values is a set of values within a Result. The order of values is not
// guaranteed to be in document order, and may be different each time a query is
// executed.
func (r Result) Values() []interface{} {
return r.items
}
// Positions is a set of positions for values within a Result. Each index
// in Positions() corresponds to the entry in Value() of the same index.
func (r Result) Positions() []toml.Position {
return r.positions
}
// runtime context for executing query paths
type queryContext struct {
result *Result
filters *map[string]NodeFilterFn
lastPosition toml.Position
}
// generic path functor interface
type pathFn interface {
setNext(next pathFn)
// it is the caller's responsibility to set the ctx.lastPosition before invoking call()
// node can be one of: *toml.Tree, []*toml.Tree, or a scalar
call(node interface{}, ctx *queryContext)
}
// A Query is the representation of a compiled TOML path. A Query is safe
// for concurrent use by multiple goroutines.
type Query struct {
root pathFn
tail pathFn
filters *map[string]NodeFilterFn
}
func newQuery() *Query {
return &Query{
root: nil,
tail: nil,
filters: &defaultFilterFunctions,
}
}
func (q *Query) appendPath(next pathFn) {
if q.root == nil {
q.root = next
} else {
q.tail.setNext(next)
}
q.tail = next
next.setNext(newTerminatingFn()) // init the next functor
}
// Compile compiles a TOML path expression. The returned Query can be used
// to match elements within a Tree and its descendants. See Execute.
func Compile(path string) (*Query, error) {
return parseQuery(lexQuery(path))
}
// Execute executes a query against a Tree, and returns the result of the query.
func (q *Query) Execute(tree *toml.Tree) *Result {
result := &Result{
items: []interface{}{},
positions: []toml.Position{},
}
if q.root == nil {
result.appendResult(tree, tree.GetPosition(""))
} else {
ctx := &queryContext{
result: result,
filters: q.filters,
}
ctx.lastPosition = tree.Position()
q.root.call(tree, ctx)
}
return result
}
// CompileAndExecute is a shorthand for Compile(path) followed by Execute(tree).
func CompileAndExecute(path string, tree *toml.Tree) (*Result, error) {
query, err := Compile(path)
if err != nil {
return nil, err
}
return query.Execute(tree), nil
}
// SetFilter sets a user-defined filter function. These may be used inside
// "?(..)" query expressions to filter TOML document elements within a query.
func (q *Query) SetFilter(name string, fn NodeFilterFn) {
if q.filters == &defaultFilterFunctions {
// clone the static table
q.filters = &map[string]NodeFilterFn{}
for k, v := range defaultFilterFunctions {
(*q.filters)[k] = v
}
}
(*q.filters)[name] = fn
}
var defaultFilterFunctions = map[string]NodeFilterFn{
"tree": func(node interface{}) bool {
_, ok := node.(*toml.Tree)
return ok
},
"int": func(node interface{}) bool {
_, ok := node.(int64)
return ok
},
"float": func(node interface{}) bool {
_, ok := node.(float64)
return ok
},
"string": func(node interface{}) bool {
_, ok := node.(string)
return ok
},
"time": func(node interface{}) bool {
_, ok := node.(time.Time)
return ok
},
"bool": func(node interface{}) bool {
_, ok := node.(bool)
return ok
},
}
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