package redisprovider

import (
	"bytes"
	"context"
	_ "embed"
	"encoding/json"
	"errors"
	"fmt"
	"io"

	"github.com/redis/go-redis/v9"

	controllerProvider "proxy-pool/internal/controller/provider"
)

type scriptReply struct {
	Status     string `json:"status"`
	Generation string `json:"generation,omitempty"`
	Epoch      uint64 `json:"epoch,string,omitempty"`
	WaitMS     int64  `json:"waitMs,omitempty"`
}

//go:embed scripts/provider.lua
var providerSource string

var providerScript = redis.NewScript(providerSource)

func runScript(ctx context.Context, client redis.Scripter, keys upstreamKeys, args ...any) (scriptReply, error) {
	var reply scriptReply
	result, err := providerScript.Run(ctx, client, keys.all(), args...).Result()
	if err != nil {
		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
			return reply, err
		}
		return reply, errors.Join(controllerProvider.ErrCoordinationUnavailable,
			fmt.Errorf("run Redis provider script: %w", err))
	}
	var payload []byte
	switch value := result.(type) {
	case string:
		payload = []byte(value)
	case []byte:
		payload = value
	default:
		return reply, errors.Join(controllerProvider.ErrCoordinationUnavailable,
			fmt.Errorf("decode Redis provider script: unexpected reply type %T", result))
	}
	decoder := json.NewDecoder(bytes.NewReader(payload))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&reply); err != nil || reply.Status == "" {
		return scriptReply{}, errors.Join(controllerProvider.ErrCoordinationUnavailable,
			fmt.Errorf("decode Redis provider script reply: %w", err))
	}
	var trailing any
	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
		return scriptReply{}, errors.Join(controllerProvider.ErrCoordinationUnavailable,
			errors.New("decode Redis provider script reply: trailing value"))
	}
	return reply, nil
}