// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

// Copyright 2017, OpenCensus Authors
//
// 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 zpages // import "go.opentelemetry.io/contrib/zpages"

import (
	"fmt"
	"html/template"
	"io"
	"log"

	"go.opentelemetry.io/contrib/zpages/internal"
)

var (
	templateFunctions = template.FuncMap{
		"even":    even,
		"spanRow": spanRowFormatter,
	}
	headerTemplate       = parseTemplate("header")
	summaryTableTemplate = parseTemplate("summary")
	tracesTableTemplate  = parseTemplate("traces")
	footerTemplate       = parseTemplate("footer")
)

// headerData contains data for the header template.
type headerData struct {
	Title string
}

func parseTemplate(name string) *template.Template {
	f, err := internal.Templates.Open("templates/" + name + ".html")
	if err != nil {
		log.Panicf("%v: %v", name, err) //nolint:revive  // Called during initialization.
	}
	defer func() {
		if err = f.Close(); err != nil {
			log.Panicf("%v: %v", name, err) //nolint:revive  // Called during initialization.
		}
	}()
	text, err := io.ReadAll(f)
	if err != nil {
		log.Panicf("%v: %v", name, err) //nolint:revive  // Called during initialization.
	}
	return template.Must(template.New(name).Funcs(templateFunctions).Parse(string(text)))
}

func spanRowFormatter(r spanRow) template.HTML {
	if !r.IsValid() {
		return ""
	}
	col := "black"
	if r.IsSampled() {
		col = "blue"
	}

	tpl := fmt.Sprintf(
		`trace_id: <b style="color:%s">%s</b> span_id: %s`,
		col,
		r.TraceID(),
		r.SpanID(),
	)
	if r.ParentSpanContext.IsValid() {
		tpl += fmt.Sprintf(` parent_span_id: %s`, r.ParentSpanContext.SpanID())
	}

	//nolint:gosec // G203: None of the dynamic attributes (TraceID/SpanID) can
	// contain characters that need escaping so this lint issue is a false
	// positive.
	return template.HTML(tpl)
}

func even(x int) bool {
	return x%2 == 0
}