// Copyright 2022 Harness Inc. All rights reserved.
// Use of this source code is governed by the Polyform Free Trial License
// that can be found in the LICENSE.md file for this repository.

package check

import (
	"fmt"
	"strings"

	"github.com/harness/gitness/types"
	"github.com/pkg/errors"
)

const (
	maxPathSegmentsForSpace = 9
	maxPathSegments         = 10
)

var (
	ErrPathEmpty = &ValidationError{
		"Path can't be empty.",
	}
	ErrPathInvalidDepth = &ValidationError{
		fmt.Sprintf("A path can have at most %d segments (%d for spaces).",
			maxPathSegments, maxPathSegmentsForSpace),
	}
	ErrEmptyPathSegment = &ValidationError{
		"Empty segments are not allowed.",
	}
	ErrPathCantBeginOrEndWithSeparator = &ValidationError{
		fmt.Sprintf("Path can't start or end with the separator ('%s').", types.PathSeparator),
	}
	ErrPathDifferentTopLevelSpace = &ValidationError{
		"Alias paths have to stay within the same top level space.",
	}
	ErrTopLevelPathNotAllowed = &ValidationError{
		"Top level alias paths are not allowed.",
	}
)

// Path checks the provided path and returns an error in it isn't valid
// NOTE: A repository path can be one deeper than a space path (as otherwise the space would be useless).
func Path(path string, isSpace bool) error {
	if path == "" {
		return ErrPathEmpty
	}

	// ensure path doesn't begin or end with /
	if path[:1] == types.PathSeparator || path[len(path)-1:] == types.PathSeparator {
		return ErrPathCantBeginOrEndWithSeparator
	}

	// ensure path is not too deep
	if err := PathDepth(path, isSpace); err != nil {
		return err
	}

	// ensure all segments of the path are valid uids
	segments := strings.Split(path, types.PathSeparator)
	for _, s := range segments {
		if s == "" {
			return ErrEmptyPathSegment
		} else if err := UID(s); err != nil {
			return errors.Wrapf(err, "Invalid segment '%s'", s)
		}
	}

	return nil
}

// PathParams validates a PathParams object that is used to create a new path.
// NOTES:
//   - We don't allow top level alias paths
//   - An alias path has to stay within the same top level space
//
// IMPORTANT:
//   - Technically there can be a racing condition when a space is being moved in between the validation and
//     path creation.
//   - But that is fine, as the path could've also been created a second earlier when it was still valid and would
//     then still exist.
func PathParams(path *types.PathParams, currentPath string, isSpace bool) error {
	// ensure the path is valid
	if err := Path(path.Path, isSpace); err != nil {
		return err
	}

	// ensure the path is at least 1 level deep (at least one '/')
	i := strings.Index(path.Path, types.PathSeparator)
	if i < 0 {
		return ErrTopLevelPathNotAllowed
	}

	// ensure the top level space doesn't change (add path separator to avoid abcd -> abc matching)
	if !strings.HasPrefix(currentPath+types.PathSeparator, path.Path[:i]+types.PathSeparator) {
		return ErrPathDifferentTopLevelSpace
	}

	return nil
}

// PathDepth Checks the depth of the provided path.
func PathDepth(path string, isSpace bool) error {
	if IsPathTooDeep(path, isSpace) {
		return ErrPathInvalidDepth
	}

	return nil
}

// IsPathTooDeep Checks if the provided path is too long.
// NOTE: A repository path can be one deeper than a space path (as otherwise the space would be useless).
func IsPathTooDeep(path string, isSpace bool) bool {
	l := strings.Count(path, types.PathSeparator) + 1
	return (!isSpace && l > maxPathSegments) || (isSpace && l > maxPathSegmentsForSpace)
}