// Copyright 2021 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package commands

import (
	"context"
	"fmt"
	"io"
	"path/filepath"
	"sort"
	"time"

	"github.com/fatih/color"

	"github.com/dolthub/dolt/go/cmd/dolt/cli"
	"github.com/dolthub/dolt/go/gen/fb/serial"
	"github.com/dolthub/dolt/go/libraries/doltcore/dbfactory"
	"github.com/dolthub/dolt/go/libraries/doltcore/env"
	"github.com/dolthub/dolt/go/libraries/utils/argparser"
	"github.com/dolthub/dolt/go/libraries/utils/filesys"
	"github.com/dolthub/dolt/go/store/chunks"
	"github.com/dolthub/dolt/go/store/nbs"
	"github.com/dolthub/dolt/go/store/prolly/tree"
	"github.com/dolthub/dolt/go/store/spec"
	"github.com/dolthub/dolt/go/store/types"
)

const numFilesParam = "numfiles"

type RootsCmd struct {
}

// Name is returns the name of the Dolt cli command. This is what is used on the command line to invoke the command
func (cmd RootsCmd) Name() string {
	return "roots"
}

// Hidden should return true if this command should be hidden from the help text
func (cmd RootsCmd) Hidden() bool {
	return true
}

// Description returns a description of the command
func (cmd RootsCmd) Description() string {
	return "Displays store root values (or potential store root values) that we find in the current database."
}

func (cmd RootsCmd) Docs() *cli.CommandDocumentation {
	return nil
}

func (cmd RootsCmd) ArgParser() *argparser.ArgParser {
	ap := argparser.NewArgParserWithMaxArgs(cmd.Name(), 0)
	ap.SupportsInt(numFilesParam, "n", "number", "Number of table files to scan.")
	return ap
}

// Exec executes the command
func (cmd RootsCmd) Exec(ctx context.Context, commandStr string, args []string, dEnv *env.DoltEnv, cliCtx cli.CliContext) int {
	ap := cmd.ArgParser()
	help, _ := cli.HelpAndUsagePrinters(cli.CommandDocsForCommandString(commandStr, cli.CommandDocumentationContent{}, ap))
	apr := cli.ParseArgsOrDie(ap, args, help)

	doltDir := dEnv.GetDoltDir()
	if doltDir == "" {
		cli.Println(color.YellowString("can no longer find a database on disk"))
		return 1
	}

	dir := filepath.Join(doltDir, dbfactory.DataDir)
	oldgen := filepath.Join(dir, "oldgen")
	itr, err := NewTableFileIter([]string{dir, oldgen}, dEnv.FS)

	if err != nil {
		return BuildVerrAndExit("Unable to read table files.", err)
	}

	n := apr.GetIntOrDefault(numFilesParam, len(itr.files))
	for i := 0; i < n; i++ {
		fPath, modified := itr.next()
		err = cmd.processTableFile(ctx, fPath, modified, dEnv.FS)

		if err == io.EOF {
			break
		} else if err != nil {
			cli.Println(color.YellowString("Failed to process '%s'. Cause: %v", fPath, err))
		}
	}

	return 0
}

func (cmd RootsCmd) processTableFile(ctx context.Context, path string, modified time.Time, fs filesys.Filesys) error {
	cli.Printf("Processing '%s' last modified: %v\n", path, modified)
	rdCloser, err := fs.OpenForRead(path)

	if err != nil {
		return err
	}

	defer rdCloser.Close()

	return nbs.IterChunks(ctx, rdCloser.(io.ReadSeeker), func(chunk chunks.Chunk) (stop bool, err error) {
		// Want a clean db every loop
		sp, _ := spec.ForDatabase("mem")
		vrw := sp.GetVRW(ctx)

		value, err := types.DecodeValue(chunk, vrw)

		if err != nil {
			return false, err
		}

		if sm, ok := value.(types.SerialMessage); ok {
			if serial.GetFileID(sm) == serial.StoreRootFileID {
				msg, err := serial.TryGetRootAsStoreRoot([]byte(sm), serial.MessagePrefixSz)
				if err != nil {
					return false, err
				}
				ambytes := msg.AddressMapBytes()
				node, fileId, err := tree.NodeFromBytes(ambytes)
				if err != nil {
					return false, err
				}
				if fileId != serial.AddressMapFileID {
					return false, fmt.Errorf("unexpected file ID for address map, expected %s, found %s", serial.AddressMapFileID, fileId)
				}
				err = tree.OutputAddressMapNode(cli.OutStream, node)
				if err != nil {
					return false, err
				}
				cli.Println()
			}
		} else {
			return false, fmt.Errorf("unexpected value type found in table file: %T", value)
		}

		return false, nil
	})
}

type fileAndTime struct {
	Path     string
	Modified time.Time
}

type TableFileIter struct {
	files []fileAndTime
	pos   int
}

func NewTableFileIter(dirs []string, fs filesys.Filesys) (*TableFileIter, error) {
	var tableFiles []fileAndTime
	for _, dir := range dirs {
		err := fs.Iter(dir, false, func(path string, size int64, isDir bool) (stop bool) {
			if !isDir {
				filename := filepath.Base(path)

				if len(filename) == 32 {
					t, ok := fs.LastModified(path)
					if !ok {
						t = time.Now()
					}

					tableFiles = append(tableFiles, fileAndTime{path, t})
				}
			}

			return false
		})

		if err != nil {
			return nil, err
		}
	}

	if len(tableFiles) == 0 {
		return nil, fmt.Errorf("No table files found in '%v'", dirs)
	}

	sort.Slice(tableFiles, func(i, j int) bool {
		return tableFiles[i].Modified.Sub(tableFiles[j].Modified) > 0
	})

	return &TableFileIter{tableFiles, 0}, nil
}

func (itr *TableFileIter) next() (string, time.Time) {
	if itr.pos >= len(itr.files) {
		return "", time.Time{}
	}

	curr := itr.files[itr.pos]
	itr.pos++

	return curr.Path, curr.Modified
}