// Copyright 2024 TheFox0x7. All rights reserved.
// SPDX-License-Identifier: EUPL-1.2

package opentelemetry

import (
	"context"
	"net/url"
	"strings"

	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/resource"
	semconv "go.opentelemetry.io/otel/semconv/v1.25.0"
)

const (
	decoderTelemetrySdk = "sdk"
	decoderProcess      = "process"
	decoderOS           = "os"
	decoderHost         = "host"
)

func newResource(ctx context.Context) (*resource.Resource, error) {
	opts := []resource.Option{
		resource.WithAttributes(parseSettingAttributes(setting.OpenTelemetry.ResourceAttributes)...),
	}
	opts = append(opts, parseDecoderOpts()...)
	opts = append(opts, resource.WithAttributes(
		semconv.ServiceName(setting.OpenTelemetry.ServiceName),
		semconv.ServiceVersion(setting.ForgejoVersion),
	))
	return resource.New(ctx, opts...)
}

func parseDecoderOpts() []resource.Option {
	var opts []resource.Option
	for _, v := range strings.Split(setting.OpenTelemetry.ResourceDetectors, ",") {
		switch v {
		case decoderTelemetrySdk:
			opts = append(opts, resource.WithTelemetrySDK())
		case decoderProcess:
			opts = append(opts, resource.WithProcess())
		case decoderOS:
			opts = append(opts, resource.WithOS())
		case decoderHost:
			opts = append(opts, resource.WithHost())
		case "": // Don't warn on empty string
		default:
			log.Warn("Ignoring unknown resource decoder option: %s", v)
		}
	}
	return opts
}

func parseSettingAttributes(s string) []attribute.KeyValue {
	var attrs []attribute.KeyValue
	rawAttrs := strings.TrimSpace(s)

	if rawAttrs == "" {
		return attrs
	}

	pairs := strings.Split(rawAttrs, ",")

	var invalid []string
	for _, p := range pairs {
		k, v, found := strings.Cut(p, "=")
		if !found {
			invalid = append(invalid, p)
			continue
		}
		key := strings.TrimSpace(k)
		val, err := url.PathUnescape(strings.TrimSpace(v))
		if err != nil {
			// Retain original value if decoding fails, otherwise it will be
			// an empty string.
			val = v
			log.Warn("Otel resource attribute decoding error, retaining unescaped value. key=%s, val=%s", key, val)
		}
		attrs = append(attrs, attribute.String(key, val))
	}
	if len(invalid) > 0 {
		log.Warn("Partial resource, missing values: %v", invalid)
	}

	return attrs
}