package restore

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/influxdata/influx-cli/v2/api"
	"github.com/influxdata/influx-cli/v2/clients"
	br "github.com/influxdata/influx-cli/v2/internal/backup_restore"
	"github.com/influxdata/influx-cli/v2/pkg/gzip"
)

type Client struct {
	clients.CLI
	api.RestoreApi
	api.OrganizationsApi

	manifest br.Manifest
}

type Params struct {
	// Path to local backup data created using `influx backup`
	Path string

	// Original ID/name of the organization to restore.
	// If not set, all orgs will be restored.
	OrgID string
	Org   string

	// New name to use for the restored organization.
	// If not set, the org will be restored using its backed-up name.
	NewOrgName string

	// Original ID/name of the bucket to restore.
	// If not set, all buckets within the org filter will be restored.
	BucketID string
	Bucket   string

	// New name to use for the restored bucket.
	// If not set, the bucket will be restored using its backed-up name.
	NewBucketName string

	// If true, replace all data on the server with the local backup.
	// Otherwise only restore the requested org/bucket, leaving other data untouched.
	Full bool
}

func (p *Params) matches(bkt br.ManifestBucketEntry) bool {
	if p.OrgID != "" && bkt.OrganizationID != p.OrgID {
		return false
	}
	if p.Org != "" && bkt.OrganizationName != p.Org {
		return false
	}
	if p.BucketID != "" && bkt.BucketID != p.BucketID {
		return false
	}
	if p.Bucket != "" && bkt.BucketName != p.Bucket {
		return false
	}
	return true
}

func (c *Client) Restore(ctx context.Context, params *Params) error {
	if err := c.loadManifests(params.Path); err != nil {
		return err
	}
	if params.Full {
		return c.fullRestore(ctx, params.Path)
	}
	return c.partialRestore(ctx, params)
}

// loadManifests finds and merges all backup manifests stored in a given directory,
// keeping the latest top-level metadata and latest metadata per-bucket.
func (c *Client) loadManifests(path string) error {
	// Read all manifest files from path, sort in ascending time.
	manifests, err := filepath.Glob(filepath.Join(path, fmt.Sprintf("*.%s", br.ManifestExtension)))
	if err != nil {
		return fmt.Errorf("failed to find backup manifests at %q: %w", path, err)
	} else if len(manifests) == 0 {
		return fmt.Errorf("no backup manifests found at %q", path)
	}
	sort.Strings(manifests)

	bucketManifests := map[string]br.ManifestBucketEntry{}
	for _, manifestFile := range manifests {
		// Skip file if it is a directory.
		if fi, err := os.Stat(manifestFile); err != nil {
			return fmt.Errorf("failed to inspect local manifest at %q: %w", manifestFile, err)
		} else if fi.IsDir() {
			continue
		}

		var manifest br.Manifest
		if buf, err := os.ReadFile(manifestFile); err != nil {
			return fmt.Errorf("failed to read local manifest at %q: %w", manifestFile, err)
		} else if err := json.Unmarshal(buf, &manifest); err != nil {
			return fmt.Errorf("failed to parse manifest at %q: %w", manifestFile, err)
		}

		// Keep the latest KV and SQL overall.
		c.manifest.KV = manifest.KV
		c.manifest.SQL = manifest.SQL

		// Keep the latest manifest per-bucket.
		for _, bkt := range manifest.Buckets {
			bucketManifests[bkt.BucketID] = bkt
		}
	}

	c.manifest.Buckets = make([]br.ManifestBucketEntry, 0, len(bucketManifests))
	for _, bkt := range bucketManifests {
		c.manifest.Buckets = append(c.manifest.Buckets, bkt)
	}

	return nil
}

func (c Client) fullRestore(ctx context.Context, path string) error {
	// Make sure we can read both local metadata snapshots before
	kvBytes, err := c.readFileGzipped(path, c.manifest.KV)
	if err != nil {
		return fmt.Errorf("failed to open local KV backup at %q: %w", filepath.Join(path, c.manifest.KV.FileName), err)
	}
	defer kvBytes.Close()
	sqlBytes, err := c.readFileGzipped(path, c.manifest.SQL)
	if err != nil {
		return fmt.Errorf("failed to open local SQL backup at %q: %w", filepath.Join(path, c.manifest.SQL.FileName), err)
	}
	defer sqlBytes.Close()

	// Upload metadata snapshots to the server.
	log.Println("INFO: Restoring KV snapshot")
	if err := c.PostRestoreKV(ctx).
		ContentEncoding("gzip").
		ContentType("application/octet-stream").
		Body(kvBytes).
		Execute(); err != nil {
		return fmt.Errorf("failed to restore KV snapshot: %w", err)
	}
	log.Println("INFO: Restoring SQL snapshot")
	if err := c.PostRestoreSQL(ctx).
		ContentEncoding("gzip").
		ContentType("application/octet-stream").
		Body(sqlBytes).
		Execute(); err != nil {
		return fmt.Errorf("failed to restore SQL snapshot: %w", err)
	}

	// Drill down through bucket manifests to reach shard info, and upload it.
	for _, b := range c.manifest.Buckets {
		for _, rp := range b.RetentionPolicies {
			for _, sg := range rp.ShardGroups {
				for _, s := range sg.Shards {
					if err := c.restoreShard(ctx, path, s); err != nil {
						return err
					}
				}
			}
		}
	}

	return nil
}

func (c Client) partialRestore(ctx context.Context, params *Params) (err error) {
	orgIds := map[string]string{}

	for _, bkt := range c.manifest.Buckets {
		// Skip internal buckets.
		if strings.HasPrefix(bkt.BucketName, "_") {
			continue
		}
		if !params.matches(bkt) {
			continue
		}

		orgName := bkt.OrganizationName
		// Before this method is called, we ensure that new-org-name is only set if
		// a filter on org-name or org-id is set. If that check passes and execution
		// reaches this code, we can assume that all buckets matching the filter come
		// from the same org, so we can swap in the new org name unconditionally.
		if params.NewOrgName != "" {
			orgName = params.NewOrgName
		}

		if _, ok := orgIds[orgName]; !ok {
			orgIds[orgName], err = c.restoreOrg(ctx, orgName)
			if err != nil {
				return
			}
		}
		bkt.OrganizationName = orgName
		bkt.OrganizationID = orgIds[orgName]

		// By the same reasoning as above, if new-bucket-name is non-empty we know
		// filters must have been set to ensure we only match 1 bucket, so we can
		// swap the name without additional checks.
		if params.NewBucketName != "" {
			bkt.BucketName = params.NewBucketName
		}

		log.Printf("INFO: Restoring bucket %q as %q\n", bkt.BucketID, bkt.BucketName)
		bucketMapping, err := c.PostRestoreBucketMetadata(ctx).
			BucketMetadataManifest(ConvertBucketManifest(bkt)).
			Execute()
		if err != nil {
			return fmt.Errorf("failed to restore bucket %q: %w", bkt.BucketName, err)
		}

		shardIdMap := make(map[int64]int64, len(bucketMapping.ShardMappings))
		for _, mapping := range bucketMapping.ShardMappings {
			shardIdMap[mapping.OldId] = mapping.NewId
		}

		for _, rp := range bkt.RetentionPolicies {
			for _, sg := range rp.ShardGroups {
				for _, sh := range sg.Shards {
					newID, ok := shardIdMap[sh.ID]
					if !ok {
						log.Printf("WARN: Server didn't map ID for shard %d in bucket %q, skipping\n", sh.ID, bkt.BucketName)
						continue
					}
					sh.ID = newID
					if err := c.restoreShard(ctx, params.Path, sh); err != nil {
						return err
					}
				}
			}
		}
	}

	return nil
}

// restoreOrg gets the ID for the org with the given name, creating the org if it doesn't already exist.
func (c Client) restoreOrg(ctx context.Context, name string) (string, error) {
	// NOTE: Our orgs API returns a 404 instead of an empty list when filtering by a specific name.
	orgs, err := c.GetOrgs(ctx).Org(name).Execute()
	if err != nil {
		if apiErr, ok := err.(api.ApiError); !ok || apiErr.ErrorCode() != api.ERRORCODE_NOT_FOUND {
			return "", fmt.Errorf("failed to check existence of organization %q: %w", name, err)
		}
	}

	// If we've gotten this far and err != nil, it means err was a 404.
	if err != nil || len(orgs.GetOrgs()) == 0 {
		// Create any missing orgs.
		newOrg, err := c.PostOrgs(ctx).PostOrganizationRequest(api.PostOrganizationRequest{Name: name}).Execute()
		if err != nil {
			return "", fmt.Errorf("failed to create organization %q: %w", name, err)
		}
		return *newOrg.Id, nil
	}

	return *orgs.GetOrgs()[0].Id, nil
}

// readFileGzipped opens a local file and returns a reader of its contents,
// compressed with gzip.
func (c Client) readFileGzipped(path string, file br.ManifestFileEntry) (io.ReadCloser, error) {
	fullPath := filepath.Join(path, file.FileName)
	f, err := os.Open(fullPath)
	if err != nil {
		return nil, err
	}
	if file.Compression == br.GzipCompression {
		return f, nil
	}
	return gzip.NewGzipPipe(f), nil
}

func (c Client) restoreShard(ctx context.Context, path string, m br.ManifestShardEntry) error {
	// Make sure we can read the local snapshot.
	tsmBytes, err := c.readFileGzipped(path, m.ManifestFileEntry)
	if err != nil {
		return fmt.Errorf("failed to open local TSM snapshot at %q: %w", filepath.Join(path, m.FileName), err)
	}
	defer tsmBytes.Close()

	log.Printf("INFO: Restoring TSM snapshot for shard %d\n", m.ID)
	if err := c.PostRestoreShardId(ctx, fmt.Sprintf("%d", m.ID)).
		ContentEncoding("gzip").
		ContentType("application/octet-stream").
		Body(tsmBytes).
		Execute(); err != nil {
		return fmt.Errorf("failed to restore TSM snapshot for shard %d: %w", m.ID, err)
	}
	return nil
}