/*
Copyright © 2026 Thomas von Dein

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package es

import (
	"context"
	"errors"
	"fmt"
	"log"
	"log/slog"
	"regexp"

	"codeberg.org/scip/esctl/pkg/cfg"
	"github.com/elastic/go-elasticsearch/v9/typedapi/cluster/health"
	"github.com/elastic/go-elasticsearch/v9/typedapi/types"
)

const (
	DefaultExclude = `(part|monitoring|.internal|metrics-endpoint)`
)

type ClusterIndices map[string]map[string]*types.IndicesRecord

func ClusterCompare(conf *cfg.Config, leader, follower string) error {
	if !checkClusterFollower(conf, leader) {
		return errors.New("leader/follower attribution is invalid, reverse cluster attribution and retry")
	}

	indices := ClusterIndices{}

	for _, alias := range []string{leader, follower} {
		cat := conf.Clusters[alias].ES.Cat.Indices().
			// we need to add custom request headers, required for older ES instances
			Header("content-type", "application/json").
			Header("accept", "application/json")

		res, err := cat.Do(context.Background())
		if err != nil {
			return fmt.Errorf("failed to get indicies on %s: %s", alias, err)
		}

		indices[alias] = make(map[string]*types.IndicesRecord, len(res))

		for _, index := range res {
			indices[alias][*index.Index] = &index
		}
	}

	if !checkClusterStatus(conf, leader, follower) {
		return errors.New("One of the two clusters is in a failed state")
	}

	findIlmErrors(conf, leader, follower)

	if findIndicesOnlyOnLeader(conf, indices, leader, follower) &&
		findOrphanedIndices(conf, indices, leader, follower) &&
		findFailedFollowerIndices(conf, indices, follower) {
		fmt.Println("everything's hunky-dory.")
	}

	return nil
}

func List(conf *cfg.Config) error {
	table := NewTable(2, len(conf.Clusters))
	table.Addheaders("cluster", "uri")

	idx := 0
	for name, cluster := range conf.Clusters {
		table.entries[idx] = []string{name, cluster.Uri}
		idx++
	}

	table.PrintMarkdown()

	return nil
}

func Status(conf *cfg.Config) error {
	clusters := []string{}

	if conf.All {
		for key, _ := range conf.Clusters {
			clusters = append(clusters, key)
		}
	} else {
		clusters = []string{"default"}
	}

	for _, cluster := range clusters {
		es := conf.DefaultCluster.ES
		if cluster != "default" {
			es = conf.Clusters[cluster].ES
		}

		res, err := es.Cluster.Health().
			Header("content-type", "application/json").
			Header("accept", "application/json").
			Do(context.Background())
		if err != nil {
			log.Fatalf("Error getting health: %s", err)
		}

		slog.Debug("ES result", "cluster health", res)

		table := NewTable(2, 5)
		table.Addheaders(cluster, "status")

		table.entries = [][]string{
			{"Cluster Name", Colorize(*&res.Status.Name, res.ClusterName)},
			{"Active Shards", fmt.Sprintf("%d", res.ActiveShards)},
			{"Active Primary Shards", fmt.Sprintf("%d", res.ActivePrimaryShards)},
			{"Indicies", fmt.Sprintf("%d", len(res.Indices))},
			{"Nodes", fmt.Sprintf("%d", res.NumberOfNodes)},
		}

		table.PrintMarkdown()
	}

	return nil
}

// look for indicies only on leader
func findIndicesOnlyOnMaster(conf *cfg.Config, indices ClusterIndices, leader, follower string) {
	exclude := regexp.MustCompile(DefaultExclude)
	if conf.Exclude != "" {
		exclude = regexp.MustCompile(conf.Exclude)
	}

	indexOnlyOnLeader := map[string]*types.IndicesRecord{}
	for name, index := range indices[leader] {
		if exclude.MatchString(name) {
			continue
		}

		_, followerHasIt := indices[follower][name]
		if !followerHasIt {
			// fetch index details
			res, err := conf.Clusters[leader].ES.Indices.Get(name).
				Header("content-type", "application/json").
				Header("accept", "application/json").
				Do(context.Background())
			if err != nil {
				continue // ignore it then
			}

			_, defined := res[name]
			if !defined {
				// json response map didn't contain the index
				continue
			}

			isWritable := false
			for _, alias := range res[name].Aliases {
				if *alias.IsWriteIndex {
					isWritable = true
					break
				}
			}

			if isWritable {
				// ignore index if associated alias index is writing
				continue
			}

			indexOnlyOnLeader[name] = index
		}
	}

	idx := 0
	table := NewTable(3, len(indexOnlyOnLeader))
	table.Addheaders("index only on leader", "size", "docscount")

	for name, index := range indexOnlyOnLeader {
		name := Colorize("red", name)

		table.entries[idx] = []string{name, *index.DatasetSize, *index.DocsCount}
		idx++
	}

	table.Sort()
	table.PrintMarkdown()
}

func checkClusterFollower(conf *cfg.Config, leader string) bool {
	stats, err := conf.Clusters[leader].ES.Ccr.Stats().
		Header("content-type", "application/json").
		Header("accept", "application/json").
		Do(context.Background())
	if err != nil {
		fmt.Printf("failed to get ccr stats from %s: %s", leader, err)
		return false
	}

	if len(stats.AutoFollowStats.AutoFollowedClusters) == 0 {
		// is not following anyone
		return true
	}

	if stats.AutoFollowStats.AutoFollowedClusters[0].ClusterName != "" {
		fmt.Println("leader/follower attribution is invalid, reverse cluster attribution and retry")
		return false
	}

	return true
}

// checks if both clusters are green
func checkClusterStatus(conf *cfg.Config, leader, follower string) bool {
	status := map[string]*health.Response{}

	for _, cluster := range []string{leader, follower} {
		st, err := conf.Clusters[leader].ES.Cluster.Health().
			Header("content-type", "application/json").
			Header("accept", "application/json").
			Do(context.Background())
		if err != nil {
			fmt.Printf("failed to get health from %s: %s", cluster, err)
			return false
		}

		status[cluster] = st
	}

	table := NewTable(3, 5)

	table.Addheaders("setting", "leader:"+leader, "follower:"+follower)

	table.entries = [][]string{
		{"Cluster Name",
			Colorize(*&status[leader].Status.Name, status[leader].ClusterName),
			Colorize(*&status[follower].Status.Name, status[follower].ClusterName),
		},
		{"Active Shards",
			fmt.Sprintf("%d", status[leader].ActiveShards),
			fmt.Sprintf("%d", status[follower].ActiveShards),
		},
		{"Active Primary Shards",
			fmt.Sprintf("%d", status[leader].ActivePrimaryShards),
			fmt.Sprintf("%d", status[follower].ActivePrimaryShards),
		},
		{"Indicies",
			fmt.Sprintf("%d", len(status[leader].Indices)),
			fmt.Sprintf("%d", len(status[follower].Indices)),
		},
		{"Nodes",
			fmt.Sprintf("%d", status[leader].NumberOfNodes),
			fmt.Sprintf("%d", status[follower].NumberOfNodes),
		},
	}

	table.PrintMarkdown()

	if status[leader].Status.Name == "green" && status[follower].Status.Name == "green" {
		return true
	}

	return false
}

// finds indices on both clusters which have ilm errors
func findIlmErrors(conf *cfg.Config, leader, follower string) bool {
	failed := map[string]map[string]string{}

	for _, cluster := range []string{leader, follower} {
		ilm, err := conf.Clusters[cluster].ES.Ilm.ExplainLifecycle("_all").
			OnlyManaged(true).
			Header("content-type", "application/json").
			Header("accept", "application/json").
			Do(context.Background())
		if err != nil {
			fmt.Printf("failed to get ilm status from %s: %s", cluster, err)
			return false
		}

		failed[cluster] = map[string]string{}

		for name, ilmstate := range ilm.Indices {
			count := ilmstate.(*types.LifecycleExplainManaged).FailedStepRetryCount

			if count != nil && *count > 0 {
				failed[cluster][name] = fmt.Sprintf("%d", *count)
			}
		}
	}

	if len(failed[leader]) == 0 && len(failed[follower]) == 0 {
		return true
	}

	for idx, cluster := range []string{leader, follower} {
		which := "leader"
		if idx > 0 {
			which = "follower"
		}

		if len(failed[cluster]) > 0 {
			idx := 0
			table := NewTable(2, len(failed[cluster]))
			table.Addheaders("ilm errors on "+which, "errors")

			for name, count := range failed[cluster] {
				table.entries[idx] = []string{name, count}
				idx++
			}

			table.Sort()
			table.PrintMarkdown()
		}
	}

	return false
}

// find unsynchronized indicies only present on leader
func findIndicesOnlyOnLeader(conf *cfg.Config, indices ClusterIndices, leader, follower string) bool {
	exclude := regexp.MustCompile(DefaultExclude)
	if conf.Exclude != "" {
		exclude = regexp.MustCompile(conf.Exclude)
	}

	indexOnlyOnLeader := map[string]*types.IndicesRecord{}
	for name, index := range indices[leader] {
		if exclude.MatchString(name) {
			continue
		}

		_, followerHasIt := indices[follower][name]
		if !followerHasIt {
			// fetch index details
			res, err := conf.Clusters[leader].ES.Indices.Get(name).
				Header("content-type", "application/json").
				Header("accept", "application/json").
				Do(context.Background())
			if err != nil {
				continue // ignore it then
			}

			_, defined := res[name]
			if !defined {
				// json response map didn't contain the index
				continue
			}

			isWritable := false
			for _, alias := range res[name].Aliases {
				if *alias.IsWriteIndex {
					isWritable = true
					break
				}
			}

			if isWritable {
				// ignore index if associated alias index is writing
				continue
			}

			indexOnlyOnLeader[name] = index
		}
	}

	if len(indexOnlyOnLeader) == 0 {
		return true
	}

	idx := 0
	table := NewTable(3, len(indexOnlyOnLeader))
	table.Addheaders("index only on leader", "size", "docscount")

	for name, index := range indexOnlyOnLeader {
		name := Colorize("red", name)

		table.entries[idx] = []string{name, *index.DatasetSize, *index.DocsCount}
		idx++
	}

	table.Sort()
	table.PrintMarkdown()

	return false
}

// find indices only present on follower
func findOrphanedIndices(conf *cfg.Config, indices ClusterIndices, leader, follower string) bool {
	orphaned := map[string]*types.IndicesRecord{}

	for name, index := range indices[follower] {
		_, leaderHasIt := indices[leader][name]
		if !leaderHasIt {
			// fetch index details
			res, err := conf.Clusters[follower].ES.Indices.Get(name).
				Header("content-type", "application/json").
				Header("accept", "application/json").
				Do(context.Background())
			if err != nil {
				continue // ignore it then
			}

			_, defined := res[name]
			if !defined {
				// json response map didn't contain the index
				continue
			}

			orphaned[name] = index
		}
	}

	if len(orphaned) == 0 {
		return true
	}

	idx := 0
	table := NewTable(3, len(orphaned))
	table.Addheaders("orphaned index on follower", "size", "docscount")

	for name, index := range orphaned {
		name := Colorize("red", name)

		table.entries[idx] = []string{name, *index.DatasetSize, *index.DocsCount}
		idx++
	}

	table.Sort()
	table.PrintMarkdown()

	return false
}

// find red indices on follower
func findFailedFollowerIndices(conf *cfg.Config, indices ClusterIndices, follower string) bool {
	red := map[string]*types.IndicesRecord{}

	for name, index := range indices[follower] {
		if *index.Health == "red" {
			red[name] = index
		}
	}

	if len(red) == 0 {
		return true
	}

	idx := 0
	table := NewTable(3, len(red))
	table.Addheaders("red index on follower", "size", "docscount")

	for name, index := range red {
		name := Colorize("red", name)

		table.entries[idx] = []string{name, *index.DatasetSize, *index.DocsCount}
		idx++
	}

	table.Sort()
	table.PrintMarkdown()

	return false
}