Make filtering a linear operation.

Improves the current filtering implementation complixity.
Currently, the best case is O(N) and worst case O(N^2) for key-value filtering.
In the new implementation, the best case is O(1) and worst case O(N), again for key-value filtering.

Signed-off-by: David Calavera <david.calavera@gmail.com>

parsers/filters/parse.go

@@ -5,6 +5,7 @@ package filters
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"regexp"
 	"strings"
 )
@@ -15,7 +16,14 @@ import (
 // in an slice.
 // e.g given -f 'label=label1=1' -f 'label=label2=2' -f 'image.name=ubuntu'
 // the args will be {'label': {'label1=1','label2=2'}, 'image.name', {'ubuntu'}}
-type Args map[string][]string
+type Args struct {
+	fields map[string]map[string]bool
+}
+
+// NewArgs initializes a new Args struct.
+func NewArgs() Args {
+	return Args{fields: map[string]map[string]bool{}}
+}
 
 // ParseFlag parses the argument to the filter flag. Like
 //
@@ -25,9 +33,6 @@ type Args map[string][]string
 // map is created.
 func ParseFlag(arg string, prev Args) (Args, error) {
 	filters := prev
-	if prev == nil {
-		filters = Args{}
-	}
 	if len(arg) == 0 {
 		return filters, nil
 	}
@@ -37,9 +42,11 @@ func ParseFlag(arg string, prev Args) (Args, error) {
 	}
 
 	f := strings.SplitN(arg, "=", 2)
+
 	name := strings.ToLower(strings.TrimSpace(f[0]))
 	value := strings.TrimSpace(f[1])
-	filters[name] = append(filters[name], value)
+
+	filters.Add(name, value)
 
 	return filters, nil
 }
@@ -50,11 +57,11 @@ var ErrBadFormat = errors.New("bad format of filter (expected name=value)")
 // ToParam packs the Args into an string for easy transport from client to server.
 func ToParam(a Args) (string, error) {
 	// this way we don't URL encode {}, just empty space
-	if len(a) == 0 {
+	if a.Len() == 0 {
 		return "", nil
 	}
 
-	buf, err := json.Marshal(a)
+	buf, err := json.Marshal(a.fields)
 	if err != nil {
 		return "", err
 	}
@@ -63,23 +70,71 @@ func ToParam(a Args) (string, error) {
 
 // FromParam unpacks the filter Args.
 func FromParam(p string) (Args, error) {
-	args := Args{}
 	if len(p) == 0 {
-		return args, nil
+		return NewArgs(), nil
 	}
-	if err := json.NewDecoder(strings.NewReader(p)).Decode(&args); err != nil {
-		return nil, err
+
+	r := strings.NewReader(p)
+	d := json.NewDecoder(r)
+
+	m := map[string]map[string]bool{}
+	if err := d.Decode(&m); err != nil {
+		r.Seek(0, 0)
+
+		// Allow parsing old arguments in slice format.
+		// Because other libraries might be sending them in this format.
+		deprecated := map[string][]string{}
+		if deprecatedErr := d.Decode(&deprecated); deprecatedErr == nil {
+			m = deprecatedArgs(deprecated)
+		} else {
+			return NewArgs(), err
+		}
 	}
-	return args, nil
+	return Args{m}, nil
+}
+
+// Get returns the list of values associates with a field.
+// It returns a slice of strings to keep backwards compatibility with old code.
+func (filters Args) Get(field string) []string {
+	values := filters.fields[field]
+	if values == nil {
+		return make([]string, 0)
+	}
+	slice := make([]string, 0, len(values))
+	for key := range values {
+		slice = append(slice, key)
+	}
+	return slice
+}
+
+// Add adds a new value to a filter field.
+func (filters Args) Add(name, value string) {
+	if _, ok := filters.fields[name]; ok {
+		filters.fields[name][value] = true
+	} else {
+		filters.fields[name] = map[string]bool{value: true}
+	}
+}
+
+// Del removes a value from a filter field.
+func (filters Args) Del(name, value string) {
+	if _, ok := filters.fields[name]; ok {
+		delete(filters.fields[name], value)
+	}
+}
+
+// Len returns the number of fields in the arguments.
+func (filters Args) Len() int {
+	return len(filters.fields)
 }
 
 // MatchKVList returns true if the values for the specified field maches the ones
 // from the sources.
 // e.g. given Args are {'label': {'label1=1','label2=1'}, 'image.name', {'ubuntu'}},
-//      field is 'label' and sources are {'label':{'label1=1','label2=2','label3=3'}}
+//      field is 'label' and sources are {'label1': '1', 'label2': '2'}
 //      it returns true.
 func (filters Args) MatchKVList(field string, sources map[string]string) bool {
-	fieldValues := filters[field]
+	fieldValues := filters.fields[field]
 
 	//do not filter if there is no filter set or cannot determine filter
 	if len(fieldValues) == 0 {
@@ -90,21 +145,16 @@ func (filters Args) MatchKVList(field string, sources map[string]string) bool {
 		return false
 	}
 
-outer:
-	for _, name2match := range fieldValues {
+	for name2match := range fieldValues {
 		testKV := strings.SplitN(name2match, "=", 2)
 
-		for k, v := range sources {
-			if len(testKV) == 1 {
-				if k == testKV[0] {
-					continue outer
-				}
-			} else if k == testKV[0] && v == testKV[1] {
-				continue outer
-			}
+		v, ok := sources[testKV[0]]
+		if !ok {
+			return false
+		}
+		if len(testKV) == 2 && testKV[1] != v {
+			return false
 		}
-
-		return false
 	}
 
 	return true
@@ -115,13 +165,12 @@ outer:
 //      field is 'image.name' and source is 'ubuntu'
 //      it returns true.
 func (filters Args) Match(field, source string) bool {
-	fieldValues := filters[field]
-
-	//do not filter if there is no filter set or cannot determine filter
-	if len(fieldValues) == 0 {
+	if filters.ExactMatch(field, source) {
 		return true
 	}
-	for _, name2match := range fieldValues {
+
+	fieldValues := filters.fields[field]
+	for name2match := range fieldValues {
 		match, err := regexp.MatchString(name2match, source)
 		if err != nil {
 			continue
@@ -132,3 +181,61 @@ func (filters Args) Match(field, source string) bool {
 	}
 	return false
 }
+
+// ExactMatch returns true if the source matches exactly one of the filters.
+func (filters Args) ExactMatch(field, source string) bool {
+	fieldValues, ok := filters.fields[field]
+	//do not filter if there is no filter set or cannot determine filter
+	if !ok || len(fieldValues) == 0 {
+		return true
+	}
+
+	// try to march full name value to avoid O(N) regular expression matching
+	if fieldValues[source] {
+		return true
+	}
+	return false
+}
+
+// Include returns true if the name of the field to filter is in the filters.
+func (filters Args) Include(field string) bool {
+	_, ok := filters.fields[field]
+	return ok
+}
+
+// Validate ensures that all the fields in the filter are valid.
+// It returns an error as soon as it finds an invalid field.
+func (filters Args) Validate(accepted map[string]bool) error {
+	for name := range filters.fields {
+		if !accepted[name] {
+			return fmt.Errorf("Invalid filter '%s'", name)
+		}
+	}
+	return nil
+}
+
+// WalkValues iterates over the list of filtered values for a field.
+// It stops the iteration if it finds an error and it returns that error.
+func (filters Args) WalkValues(field string, op func(value string) error) error {
+	if _, ok := filters.fields[field]; !ok {
+		return nil
+	}
+	for v := range filters.fields[field] {
+		if err := op(v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func deprecatedArgs(d map[string][]string) map[string]map[string]bool {
+	m := map[string]map[string]bool{}
+	for k, v := range d {
+		values := map[string]bool{}
+		for _, vv := range v {
+			values[vv] = true
+		}
+		m[k] = values
+	}
+	return m
+}