package fs

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"path"
	"path/filepath"

	"github.com/databricks/cli/cmd/root"
	"github.com/databricks/cli/libs/cmdio"
	"github.com/databricks/cli/libs/filer"
	"github.com/spf13/cobra"
)

type copy struct {
	overwrite bool
	recursive bool

	ctx          context.Context
	sourceFiler  filer.Filer
	targetFiler  filer.Filer
	sourceScheme string
	targetScheme string
}

func (c *copy) cpWriteCallback(sourceDir, targetDir string) fs.WalkDirFunc {
	return func(sourcePath string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		// Compute path relative to the target directory
		relPath, err := filepath.Rel(sourceDir, sourcePath)
		if err != nil {
			return err
		}
		relPath = filepath.ToSlash(relPath)

		// Compute target path for the file
		targetPath := path.Join(targetDir, relPath)

		// create directory and return early
		if d.IsDir() {
			return c.targetFiler.Mkdir(c.ctx, targetPath)
		}

		return c.cpFileToFile(sourcePath, targetPath)
	}
}

func (c *copy) cpDirToDir(sourceDir, targetDir string) error {
	if !c.recursive {
		return fmt.Errorf("source path %s is a directory. Please specify the --recursive flag", sourceDir)
	}

	sourceFs := filer.NewFS(c.ctx, c.sourceFiler)
	return fs.WalkDir(sourceFs, sourceDir, c.cpWriteCallback(sourceDir, targetDir))
}

func (c *copy) cpFileToDir(sourcePath, targetDir string) error {
	fileName := path.Base(sourcePath)
	targetPath := path.Join(targetDir, fileName)

	return c.cpFileToFile(sourcePath, targetPath)
}

func (c *copy) cpFileToFile(sourcePath, targetPath string) error {
	// Get reader for file at source path
	r, err := c.sourceFiler.Read(c.ctx, sourcePath)
	if err != nil {
		return err
	}
	defer r.Close()

	if c.overwrite {
		err = c.targetFiler.Write(c.ctx, targetPath, r, filer.OverwriteIfExists)
		if err != nil {
			return err
		}
	} else {
		err = c.targetFiler.Write(c.ctx, targetPath, r)
		// skip if file already exists
		if err != nil && errors.Is(err, fs.ErrExist) {
			return c.emitFileSkippedEvent(sourcePath, targetPath)
		}
		if err != nil {
			return err
		}
	}
	return c.emitFileCopiedEvent(sourcePath, targetPath)
}

// TODO: emit these events on stderr
// TODO: add integration tests for these events
func (c *copy) emitFileSkippedEvent(sourcePath, targetPath string) error {
	fullSourcePath := sourcePath
	if c.sourceScheme != "" {
		fullSourcePath = path.Join(c.sourceScheme+":", sourcePath)
	}
	fullTargetPath := targetPath
	if c.targetScheme != "" {
		fullTargetPath = path.Join(c.targetScheme+":", targetPath)
	}

	event := newFileSkippedEvent(fullSourcePath, fullTargetPath)
	template := "{{.SourcePath}} -> {{.TargetPath}} (skipped; already exists)\n"

	return cmdio.RenderWithTemplate(c.ctx, event, template)
}

func (c *copy) emitFileCopiedEvent(sourcePath, targetPath string) error {
	fullSourcePath := sourcePath
	if c.sourceScheme != "" {
		fullSourcePath = path.Join(c.sourceScheme+":", sourcePath)
	}
	fullTargetPath := targetPath
	if c.targetScheme != "" {
		fullTargetPath = path.Join(c.targetScheme+":", targetPath)
	}

	event := newFileCopiedEvent(fullSourcePath, fullTargetPath)
	template := "{{.SourcePath}} -> {{.TargetPath}}\n"

	return cmdio.RenderWithTemplate(c.ctx, event, template)
}

func newCpCommand() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "cp SOURCE_PATH TARGET_PATH",
		Short: "Copy files and directories to and from DBFS.",
		Long: `Copy files to and from DBFS.

	  For paths in DBFS it is required that you specify the "dbfs" scheme.
	  For example: dbfs:/foo/bar.

	  Recursively copying a directory will copy all files inside directory
	  at SOURCE_PATH to the directory at TARGET_PATH.

	  When copying a file, if TARGET_PATH is a directory, the file will be created
	  inside the directory, otherwise the file is created at TARGET_PATH.
	`,
		Args:    cobra.ExactArgs(2),
		PreRunE: root.MustWorkspaceClient,
	}

	var c copy
	cmd.Flags().BoolVar(&c.overwrite, "overwrite", false, "overwrite existing files")
	cmd.Flags().BoolVarP(&c.recursive, "recursive", "r", false, "recursively copy files from directory")

	cmd.RunE = func(cmd *cobra.Command, args []string) error {
		ctx := cmd.Context()

		// TODO: Error if a user uses '\' as path separator on windows when "file"
		// scheme is specified (https://github.com/databricks/cli/issues/485)

		// Get source filer and source path without scheme
		fullSourcePath := args[0]
		sourceFiler, sourcePath, err := filerForPath(ctx, fullSourcePath)
		if err != nil {
			return err
		}

		// Get target filer and target path without scheme
		fullTargetPath := args[1]
		targetFiler, targetPath, err := filerForPath(ctx, fullTargetPath)
		if err != nil {
			return err
		}

		c.sourceScheme = ""
		if isDbfsPath(fullSourcePath) {
			c.sourceScheme = "dbfs"
		}
		c.targetScheme = ""
		if isDbfsPath(fullTargetPath) {
			c.targetScheme = "dbfs"
		}

		c.ctx = ctx
		c.sourceFiler = sourceFiler
		c.targetFiler = targetFiler

		// Get information about file at source path
		sourceInfo, err := sourceFiler.Stat(ctx, sourcePath)
		if err != nil {
			return err
		}

		// case 1: source path is a directory, then recursively create files at target path
		if sourceInfo.IsDir() {
			return c.cpDirToDir(sourcePath, targetPath)
		}

		// case 2: source path is a file, and target path is a directory. In this case
		// we copy the file to inside the directory
		if targetInfo, err := targetFiler.Stat(ctx, targetPath); err == nil && targetInfo.IsDir() {
			return c.cpFileToDir(sourcePath, targetPath)
		}

		// case 3: source path is a file, and target path is a file
		return c.cpFileToFile(sourcePath, targetPath)
	}

	return cmd
}