package redisotel

import (
	"context"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
	"go.opentelemetry.io/otel/trace"

	"github.com/go-redis/redis/extra/rediscmd/v8"
	"github.com/go-redis/redis/v8"
)

const (
	// todo: consider using the full module path "github.com/go-redis/redis/extra/redisotel"
	defaultTracerName = "github.com/go-redis/redis"
)

type TracingHook struct {
	tracer trace.Tracer
}

func NewTracingHook(opts ...Option) *TracingHook {
	cfg := &config{
		tp: otel.GetTracerProvider(),
	}
	for _, opt := range opts {
		opt.apply(cfg)
	}

	tracer := cfg.tp.Tracer(
		defaultTracerName,
		// todo: consider adding a version
		// trace.WithInstrumentationVersion("semver:8.11.4"),
	)
	return &TracingHook{tracer: tracer}
}

func (th *TracingHook) BeforeProcess(ctx context.Context, cmd redis.Cmder) (context.Context, error) {
	if !trace.SpanFromContext(ctx).IsRecording() {
		return ctx, nil
	}

	opts := []trace.SpanStartOption{
		trace.WithSpanKind(trace.SpanKindClient),
		trace.WithAttributes(
			semconv.DBSystemRedis,
			semconv.DBStatementKey.String(rediscmd.CmdString(cmd)),
		),
	}

	ctx, _ = th.tracer.Start(ctx, cmd.FullName(), opts...)

	return ctx, nil
}

func (th *TracingHook) AfterProcess(ctx context.Context, cmd redis.Cmder) error {
	span := trace.SpanFromContext(ctx)
	if err := cmd.Err(); err != nil {
		recordError(ctx, span, err)
	}
	span.End()
	return nil
}

func (th *TracingHook) BeforeProcessPipeline(ctx context.Context, cmds []redis.Cmder) (context.Context, error) {
	if !trace.SpanFromContext(ctx).IsRecording() {
		return ctx, nil
	}

	summary, cmdsString := rediscmd.CmdsString(cmds)

	opts := []trace.SpanStartOption{
		trace.WithSpanKind(trace.SpanKindClient),
		trace.WithAttributes(
			semconv.DBSystemRedis,
			semconv.DBStatementKey.String(cmdsString),
			attribute.Int("db.redis.num_cmd", len(cmds)),
		),
	}

	ctx, _ = th.tracer.Start(ctx, "pipeline "+summary, opts...)

	return ctx, nil
}

func (th *TracingHook) AfterProcessPipeline(ctx context.Context, cmds []redis.Cmder) error {
	span := trace.SpanFromContext(ctx)
	if err := cmds[0].Err(); err != nil {
		recordError(ctx, span, err)
	}
	span.End()
	return nil
}

func recordError(ctx context.Context, span trace.Span, err error) {
	if err != redis.Nil {
		span.RecordError(err)
		span.SetStatus(codes.Error, err.Error())
	}
}

type config struct {
	tp trace.TracerProvider
}

// Option specifies instrumentation configuration options.
type Option interface {
	apply(*config)
}

type optionFunc func(*config)

func (o optionFunc) apply(c *config) {
	o(c)
}

// WithTracerProvider specifies a tracer provider to use for creating a tracer.
// If none is specified, the global provider is used.
func WithTracerProvider(provider trace.TracerProvider) Option {
	return optionFunc(func(cfg *config) {
		if provider != nil {
			cfg.tp = provider
		}
	})
}