implements: add a JSON based report output

Allowing the tool to generate a JSON report makes it easier to add
additional tools later to make use of this data, without hand parsing
the text output.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

contrib/implements/internal/implements/json_report.go

@@ -0,0 +1,123 @@
+package implements
+
+import (
+	"encoding/json"
+	"io"
+	"sort"
+)
+
+// JSONReport is a type that implements the Report interface and generates
+// structured JSON.
+type JSONReport struct {
+	o    ReportOptions
+	dest io.Writer
+
+	data jrOut
+}
+
+type jrFlags foundFlags
+
+func (f jrFlags) MarshalJSON() ([]byte, error) {
+	o := []string{}
+	flags := foundFlags(f)
+
+	if flags&isCalled == isCalled {
+		o = append(o, "called")
+	}
+	if flags&isDocumented == isDocumented {
+		o = append(o, "documented")
+	}
+	if flags&isDeprecated == isDeprecated {
+		o = append(o, "deprecated")
+	}
+	return json.Marshal(o)
+}
+
+type jrFunction struct {
+	CName string   `json:"c_name"`
+	Flags jrFlags  `json:"flags,omitempty"`
+	Refs  []string `json:"referenced_by,omitempty"`
+}
+
+type jrPackage struct {
+	Name    string `json:"name"`
+	Summary struct {
+		Total      int `json:"total"`
+		Found      int `json:"found"`
+		Missing    int `json:"missing"`
+		Deprecated int `json:"deprecated"`
+	} `json:"summary"`
+	Covered []jrFunction `json:"covered,omitempty"`
+	Missing []jrFunction `json:"missing,omitempty"`
+}
+
+type jrOut map[string]jrPackage
+
+// NewJSONReport creates a new json report. The JSON will be written to
+// the supplied dest when Done is called.
+func NewJSONReport(o ReportOptions, dest io.Writer) *JSONReport {
+	return &JSONReport{o, dest, jrOut{}}
+}
+
+// Report will update the JSON report with the current code inspector's state.
+func (r *JSONReport) Report(name string, ii *Inspector) error {
+	ii.update()
+
+	jp := jrPackage{}
+	total := len(ii.expected)
+	found := len(ii.found)
+	jp.Summary.Total = total
+	jp.Summary.Found = found
+	jp.Summary.Missing = total - found - ii.deprecatedMissing
+	jp.Summary.Deprecated = ii.deprecatedMissing
+	jp.Name = name
+
+	if r.o.List {
+		collectFuncs(&jp, ii)
+	}
+	r.data[name] = jp
+	return nil
+}
+
+func collectFuncs(jp *jrPackage, ii *Inspector) {
+	sort.Sort(ii.expected)
+	for _, cf := range ii.expected {
+		if flags, ok := ii.found[cf.Name]; ok {
+			refm := map[string]bool{}
+			if n := ii.visitor.callMap[cf.Name]; n != "" {
+				refm[n] = true
+			}
+			if n := ii.visitor.docMap[cf.Name]; n != "" {
+				refm[n] = true
+			}
+			jp.Covered = append(jp.Covered,
+				jrFunction{cf.Name, jrFlags(flags), mkeys(refm)})
+		}
+	}
+	for _, cf := range ii.expected {
+		if _, ok := ii.found[cf.Name]; ok {
+			continue
+		}
+		var flags jrFlags
+		if cf.isDeprecated() {
+			flags |= jrFlags(isDeprecated)
+		}
+		jp.Missing = append(jp.Missing,
+			jrFunction{cf.Name, flags, []string{}})
+	}
+}
+
+func mkeys(m map[string]bool) []string {
+	o := make([]string, 0, len(m))
+	for k := range m {
+		o = append(o, k)
+	}
+	return o
+}
+
+// Done completes the JSON report and writes the JSON to the output.
+func (r *JSONReport) Done() error {
+	enc := json.NewEncoder(r.dest)
+	enc.SetIndent("", "  ")
+	return enc.Encode(r.data)
+}