package redisactivity

import (
	"context"
	"encoding/json"
	"strconv"

	"proxy-pool/internal/domain/activitypool"
)

var _ activitypool.UpstreamDrainPolicyWriter = (*Adapter)(nil)

type upstreamDrainPolicyRecord struct {
	Version    int    `json:"version"`
	UpstreamID string `json:"upstreamId"`
	Revision   string `json:"revision"`
	Enabled    bool   `json:"enabled"`
}

func (a *Adapter) ReplaceUpstreamDrainPolicies(ctx context.Context, policies []activitypool.UpstreamDrainPolicy) error {
	if ctx == nil {
		return activitypool.ErrInvalidMaintenance
	}
	if err := ctx.Err(); err != nil {
		return err
	}
	if a == nil {
		return activitypool.ErrInvalidMaintenance
	}
	records := make([]upstreamDrainPolicyRecord, 0, len(policies))
	seen := make(map[string]struct{}, len(policies))
	for _, policy := range policies {
		if policy.UpstreamID == "" || policy.Revision == 0 {
			return activitypool.ErrInvalidMaintenance
		}
		if _, duplicate := seen[policy.UpstreamID]; duplicate {
			return activitypool.ErrInvalidMaintenance
		}
		seen[policy.UpstreamID] = struct{}{}
		records = append(records, upstreamDrainPolicyRecord{
			Version: 1, UpstreamID: policy.UpstreamID, Revision: strconv.FormatUint(policy.Revision, 10), Enabled: policy.Enabled,
		})
	}
	payload, err := json.Marshal(records)
	if err != nil {
		return err
	}
	result, err := runScript(ctx, a.client, upstreamDrainPolicyScript, []string{a.keys.upstreamDrainPolicies}, string(payload))
	if err != nil {
		return err
	}
	var reply upstreamDrainPolicyScriptReply
	if err := decodeScriptResult(result, &reply); err != nil {
		return err
	}
	if reply.Status == scriptInvalid {
		return activitypool.ErrInvalidMaintenance
	}
	if reply.Status != scriptOK {
		return invalidScriptReply("unexpected upstream drain policy reply")
	}
	return nil
}