package decorator

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"git.loyso.art/frx/kurious/internal/common/xcontext"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/trace"
)

var (
	nameAttribute = attribute.Key("cq.name")
	argsAttribute = attribute.Key("cq.args")

	apiTracer = otel.Tracer("api")
)

type commandLoggingDecorator[T any] struct {
	base CommandHandler[T]
	log  *slog.Logger
}

func (c commandLoggingDecorator[T]) Handle(ctx context.Context, cmd T) (err error) {
	handlerName := getTypeName[T]()

	ctx = xcontext.WithLogFields(ctx, slog.String("handler", handlerName))

	var argsBuilder strings.Builder
	_ = json.NewEncoder(&argsBuilder).Encode(cmd)

	var span trace.Span
	ctx, span = apiTracer.Start(ctx, "command "+handlerName)
	span.SetAttributes(
		nameAttribute.String(handlerName),
		argsAttribute.String(argsBuilder.String()),
	)

	xcontext.LogDebug(ctx, c.log, "executing command")
	start := time.Now()

	defer func() {
		elapsed := slog.Duration("elapsed", time.Since(start))
		if err == nil {
			xcontext.LogInfo(ctx, c.log, "command executed successfuly", elapsed)
		} else {
			xcontext.LogError(ctx, c.log, "command execution failed", elapsed, slog.Any("err", err))
			span.RecordError(err)
		}
		span.End()
	}()

	return c.base.Handle(ctx, cmd)
}

type queryLoggingDecorator[Q, U any] struct {
	base QueryHandler[Q, U]
	log  *slog.Logger
}

func (q queryLoggingDecorator[Q, U]) Handle(ctx context.Context, query Q) (entity U, err error) {
	handlerName := getTypeName[Q]()
	ctx = xcontext.WithLogFields(ctx, slog.String("handler", handlerName))

	var argsBuilder strings.Builder
	_ = json.NewEncoder(&argsBuilder).Encode(query)

	var span trace.Span
	ctx, span = apiTracer.Start(ctx, "query "+handlerName)
	span.SetAttributes(
		nameAttribute.String(handlerName),
		argsAttribute.String(argsBuilder.String()),
	)

	xcontext.LogDebug(ctx, q.log, "executing command")
	start := time.Now()

	defer func() {
		elapsed := slog.Duration("elapsed", time.Since(start))
		if err == nil {
			xcontext.LogInfo(ctx, q.log, "command executed successfuly", elapsed)
		} else {
			xcontext.LogError(ctx, q.log, "command execution failed", elapsed, slog.Any("err", err))
			span.RecordError(err)
		}
		now := time.Now()
		span.End(trace.WithTimestamp(now))
	}()

	return q.base.Handle(ctx, query)

}

func getTypeName[T any]() string {
	var t T
	out := fmt.Sprintf("%T", t)
	return out
}