// Copyright 2016 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package internal

import (
	"bytes"
	"encoding/json"
	"fmt"
	"regexp"
	"strings"
	"unicode/utf8"

	"google.golang.org/protobuf/types/known/structpb"
)

const (
	// ProdAddr is the production address.
	ProdAddr = "logging.googleapis.com:443"

	// TraceHeader is the HTTP header trace information is stored in.
	TraceHeader = "X-Cloud-Trace-Context"
)

// LogPath creates a formatted path from a parent and a logID.
func LogPath(parent, logID string) string {
	logID = strings.Replace(logID, "/", "%2F", -1)
	return fmt.Sprintf("%s/logs/%s", parent, logID)
}

// LogIDFromPath parses and returns the ID from a log path.
func LogIDFromPath(parent, path string) string {
	start := len(parent) + len("/logs/")
	if len(path) < start {
		return ""
	}
	logID := path[start:]
	return strings.Replace(logID, "%2F", "/", -1)
}

var reCloudTraceContext = regexp.MustCompile(
	// Matches on "TRACE_ID"
	`([a-f\d]+)?` +
		// Matches on "/SPAN_ID"
		`(?:/([a-f\d]+))?` +
		// Matches on ";0=TRACE_TRUE"
		`(?:;o=(\d))?`)

// DeconstructXCloudTraceContext extracts trace information from the trace
// header.
//
// As per the format described at https://cloud.google.com/trace/docs/setup#force-trace
//    "X-Cloud-Trace-Context: TRACE_ID/SPAN_ID;o=TRACE_TRUE"
// for example:
//    "X-Cloud-Trace-Context: 105445aa7843bc8bf206b120001000/1;o=1"
//
// We expect:
//   * traceID (optional): 			"105445aa7843bc8bf206b120001000"
//   * spanID (optional):       	"1"
//   * traceSampled (optional): 	true
func DeconstructXCloudTraceContext(s string) (traceID, spanID string, traceSampled bool) {
	matches := reCloudTraceContext.FindStringSubmatch(s)

	traceID, spanID, traceSampled = matches[1], matches[2], matches[3] == "1"

	if spanID == "0" {
		spanID = ""
	}

	return
}

// FixUTF8 is a helper that fixes an invalid UTF-8 string by replacing
// invalid UTF-8 runes with the Unicode replacement character (U+FFFD).
// See Issue https://github.com/googleapis/google-cloud-go/issues/1383.
func FixUTF8(s string) string {
	if utf8.ValidString(s) {
		return s
	}

	// Otherwise time to build the sequence.
	buf := new(bytes.Buffer)
	buf.Grow(len(s))
	for _, r := range s {
		if utf8.ValidRune(r) {
			buf.WriteRune(r)
		} else {
			buf.WriteRune('\uFFFD')
		}
	}
	return buf.String()
}

// ToProtoStruct converts v, which must marshal into a JSON object,
// into a Google Struct proto.
func ToProtoStruct(v interface{}) (*structpb.Struct, error) {
	// Fast path: if v is already a *structpb.Struct, nothing to do.
	if s, ok := v.(*structpb.Struct); ok {
		return s, nil
	}
	// v is a Go value that supports JSON marshalling. We want a Struct
	// protobuf. Some day we may have a more direct way to get there, but right
	// now the only way is to marshal the Go value to JSON, unmarshal into a
	// map, and then build the Struct proto from the map.
	var jb []byte
	var err error
	if raw, ok := v.(json.RawMessage); ok { // needed for Go 1.7 and below
		jb = []byte(raw)
	} else {
		jb, err = json.Marshal(v)
		if err != nil {
			return nil, fmt.Errorf("logging: json.Marshal: %v", err)
		}
	}
	var m map[string]interface{}
	err = json.Unmarshal(jb, &m)
	if err != nil {
		return nil, fmt.Errorf("logging: json.Unmarshal: %v", err)
	}
	return jsonMapToProtoStruct(m), nil
}

func jsonMapToProtoStruct(m map[string]interface{}) *structpb.Struct {
	fields := map[string]*structpb.Value{}
	for k, v := range m {
		fields[k] = jsonValueToStructValue(v)
	}
	return &structpb.Struct{Fields: fields}
}

func jsonValueToStructValue(v interface{}) *structpb.Value {
	switch x := v.(type) {
	case bool:
		return &structpb.Value{Kind: &structpb.Value_BoolValue{BoolValue: x}}
	case float64:
		return &structpb.Value{Kind: &structpb.Value_NumberValue{NumberValue: x}}
	case string:
		return &structpb.Value{Kind: &structpb.Value_StringValue{StringValue: x}}
	case nil:
		return &structpb.Value{Kind: &structpb.Value_NullValue{}}
	case map[string]interface{}:
		return &structpb.Value{Kind: &structpb.Value_StructValue{StructValue: jsonMapToProtoStruct(x)}}
	case []interface{}:
		var vals []*structpb.Value
		for _, e := range x {
			vals = append(vals, jsonValueToStructValue(e))
		}
		return &structpb.Value{Kind: &structpb.Value_ListValue{ListValue: &structpb.ListValue{Values: vals}}}
	default:
		return &structpb.Value{Kind: &structpb.Value_NullValue{}}
	}
}