package rule

import (
	"regexp"

	"github.com/mgechev/revive/lint"
)

// FileHeaderRule lints given else constructs.
type FileHeaderRule struct{}

var (
	multiRegexp  = regexp.MustCompile("^/\\*")
	singleRegexp = regexp.MustCompile("^//")
)

// Apply applies the rule to given file.
func (r *FileHeaderRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
	if len(arguments) != 1 {
		panic(`invalid configuration for "file-header" rule`)
	}

	header, ok := arguments[0].(string)
	if !ok {
		panic(`invalid argument for "file-header" rule: first argument should be a string`)
	}

	failure := []lint.Failure{
		{
			Node:       file.AST,
			Confidence: 1,
			Failure:    "the file doesn't have an appropriate header",
		},
	}

	if len(file.AST.Comments) == 0 {
		return failure
	}

	g := file.AST.Comments[0]
	if g == nil {
		return failure
	}
	comment := ""
	for _, c := range g.List {
		text := c.Text
		if multiRegexp.Match([]byte(text)) {
			text = text[2 : len(text)-2]
		} else if singleRegexp.Match([]byte(text)) {
			text = text[2:]
		}
		comment += text
	}

	regex, err := regexp.Compile(header)
	if err != nil {
		panic(err.Error())
	}

	if !regex.Match([]byte(comment)) {
		return failure
	}
	return nil
}

// Name returns the rule name.
func (r *FileHeaderRule) Name() string {
	return "file-header"
}