// Copyright 2023 Harness, 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 check

import (
	"errors"
	"fmt"
	"strings"
)

/* https://git-scm.com/docs/git-check-ref-format
 * How to handle various characters in refnames:
 * 0: An acceptable character for refs
 * 1: End-of-component
 * 2: ., look for a preceding . to reject .. in refs
 * 3: {, look for a preceding @ to reject @{ in refs
 * 4: A bad character: ASCII control characters, and
 *    ":", "?", "[", "\", "^", "~", SP, or TAB
 * 5: *, reject unless REFNAME_REFSPEC_PATTERN is set.
 */
var refnameDisposition = [256]byte{
	1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
	4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
	4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 2, 1,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 4,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 4, 0, 4, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 4, 4,
}

//nolint:gocognit // refactor if needed
func BranchName(branch string) error {
	const lock = ".lock"
	last := byte('\x00')

	for i := 0; i < len(branch); i++ {
		ch := branch[i] & 255
		disp := refnameDisposition[ch]

		switch disp {
		case 1:
			if i == 0 {
				goto out
			}
			if last == '/' { // Refname contains "//"
				return fmt.Errorf("branch '%s' cannot have two consecutive slashes // ", branch)
			}
		case 2:
			if last == '.' { // Refname contains ".."
				return fmt.Errorf("branch '%s' cannot have two consecutive dots .. ", branch)
			}
		case 3:
			if last == '@' { // Refname contains "@{".
				return fmt.Errorf("branch '%s' cannot contain a sequence @{", branch)
			}
		case 4:
			return fmt.Errorf("branch '%s' cannot have ASCII control characters "+
				"(i.e. bytes whose values are lower than \040, or \177 DEL), space, tilde ~, caret ^, or colon : anywhere", branch)
		case 5:
			return fmt.Errorf("branch '%s' can't be a pattern", branch)
		}
		last = ch
	}
out:
	if last == '\x00' {
		return errors.New("branch name is empty")
	}
	if last == '.' {
		return fmt.Errorf("branch '%s' cannot have . at the end", branch)
	}
	if last == '@' {
		return fmt.Errorf("branch '%s' cannot be the single character @", branch)
	}
	if last == '/' {
		return fmt.Errorf("branch '%s' cannot have / at the end", branch)
	}
	if branch[0] == '.' {
		return fmt.Errorf("branch '%s' cannot start with '.'", branch)
	}
	if strings.HasSuffix(branch, lock) {
		return fmt.Errorf("branch '%s' cannot end with '%s'", branch, lock)
	}
	return nil
}