// Copyright 2020 PingCAP, Inc. Licensed under Apache-2.0.

package pdutil

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/hex"
	"encoding/json"
	"net/http"

	"github.com/pingcap/errors"
	berrors "github.com/pingcap/tidb/br/pkg/errors"
	"github.com/pingcap/tidb/br/pkg/httputil"
	"github.com/pingcap/tidb/store/pdtypes"
	"github.com/pingcap/tidb/tablecodec"
	"github.com/pingcap/tidb/util/codec"
)

// UndoFunc is a 'undo' operation of some undoable command.
// (e.g. RemoveSchedulers).
type UndoFunc func(context.Context) error

// Nop is the 'zero value' of undo func.
var Nop UndoFunc = func(context.Context) error { return nil }

const (
	placementRuleURL = "/pd/api/v1/config/rules"
)

// GetPlacementRules return the current placement rules.
func GetPlacementRules(ctx context.Context, pdAddr string, tlsConf *tls.Config) ([]pdtypes.Rule, error) {
	cli := httputil.NewClient(tlsConf)
	prefix := "http://"
	if tlsConf != nil {
		prefix = "https://"
	}
	reqURL := prefix + pdAddr + placementRuleURL
	req, err := http.NewRequestWithContext(ctx, "GET", reqURL, nil)
	if err != nil {
		return nil, errors.Trace(err)
	}
	resp, err := cli.Do(req)
	if err != nil {
		return nil, errors.Trace(err)
	}
	defer resp.Body.Close()
	buf := new(bytes.Buffer)
	_, err = buf.ReadFrom(resp.Body)
	if err != nil {
		return nil, errors.Trace(err)
	}
	if resp.StatusCode == http.StatusPreconditionFailed {
		return []pdtypes.Rule{}, nil
	}
	if resp.StatusCode != http.StatusOK {
		return nil, errors.Annotatef(berrors.ErrPDInvalidResponse, "get placement rules failed: resp=%v, err=%v, code=%d", buf.String(), err, resp.StatusCode)
	}
	var rules []pdtypes.Rule
	err = json.Unmarshal(buf.Bytes(), &rules)
	if err != nil {
		return nil, errors.Trace(err)
	}
	return rules, nil
}

// SearchPlacementRule returns the placement rule matched to the table or nil.
func SearchPlacementRule(tableID int64, placementRules []pdtypes.Rule, role pdtypes.PeerRoleType) *pdtypes.Rule {
	for _, rule := range placementRules {
		key, err := hex.DecodeString(rule.StartKeyHex)
		if err != nil {
			continue
		}
		_, decoded, err := codec.DecodeBytes(key, nil)
		if err != nil {
			continue
		}
		if rule.Role == role && tableID == tablecodec.DecodeTableID(decoded) {
			return &rule
		}
	}
	return nil
}