package sv

import (
	"bufio"
	"fmt"
	"regexp"
	"strings"
)

const (
	breakingChangeFooterKey   = "BREAKING CHANGE"
	breakingChangeMetadataKey = "breaking-change"
	issueMetadataKey          = "issue"
	messageRegexGroupName     = "message"
)

// CommitMessage is a message using conventional commits.
type CommitMessage struct {
	Type             string            `json:"type,omitempty"`
	Scope            string            `json:"scope,omitempty"`
	Description      string            `json:"description,omitempty"`
	Body             string            `json:"body,omitempty"`
	IsBreakingChange bool              `json:"isBreakingChange,omitempty"`
	Metadata         map[string]string `json:"metadata,omitempty"`
}

// NewCommitMessage commit message constructor.
func NewCommitMessage(ctype, scope, description, body, issue, breakingChanges string) CommitMessage {
	metadata := make(map[string]string)
	if issue != "" {
		metadata[issueMetadataKey] = issue
	}
	if breakingChanges != "" {
		metadata[breakingChangeMetadataKey] = breakingChanges
	}
	return CommitMessage{Type: ctype, Scope: scope, Description: description, Body: body, IsBreakingChange: breakingChanges != "", Metadata: metadata}
}

// Issue return issue from metadata.
func (m CommitMessage) Issue() string {
	return m.Metadata[issueMetadataKey]
}

// BreakingMessage return breaking change message from metadata.
func (m CommitMessage) BreakingMessage() string {
	return m.Metadata[breakingChangeMetadataKey]
}

// MessageProcessor interface.
type MessageProcessor interface {
	SkipBranch(branch string, detached bool) bool
	Validate(message string) error
	ValidateType(ctype string) error
	ValidateScope(scope string) error
	ValidateDescription(description string) error
	Enhance(branch string, message string) (string, error)
	IssueID(branch string) (string, error)
	Format(msg CommitMessage) (string, string, string)
	Parse(subject, body string) CommitMessage
}

// NewMessageProcessor MessageProcessorImpl constructor.
func NewMessageProcessor(mcfg CommitMessageConfig, bcfg BranchesConfig) *MessageProcessorImpl {
	return &MessageProcessorImpl{
		messageCfg:  mcfg,
		branchesCfg: bcfg,
	}
}

// MessageProcessorImpl process validate message hook.
type MessageProcessorImpl struct {
	messageCfg  CommitMessageConfig
	branchesCfg BranchesConfig
}

// SkipBranch check if branch should be ignored.
func (p MessageProcessorImpl) SkipBranch(branch string, detached bool) bool {
	return contains(branch, p.branchesCfg.Skip) || (p.branchesCfg.SkipDetached != nil && *p.branchesCfg.SkipDetached && detached)
}

// Validate commit message.
func (p MessageProcessorImpl) Validate(message string) error {
	subject, body := splitCommitMessageContent(message)
	msg := p.Parse(subject, body)

	if !regexp.MustCompile(`^[a-z+]+(\(.+\))?!?: .+$`).MatchString(subject) {
		return fmt.Errorf("subject [%s] should be valid according with conventional commits", subject)
	}

	if err := p.ValidateType(msg.Type); err != nil {
		return err
	}

	if err := p.ValidateScope(msg.Scope); err != nil {
		return err
	}

	if err := p.ValidateDescription(msg.Description); err != nil {
		return err
	}

	return nil
}

// ValidateType check if commit type is valid.
func (p MessageProcessorImpl) ValidateType(ctype string) error {
	if ctype == "" || !contains(ctype, p.messageCfg.Types) {
		return fmt.Errorf("message type should be one of [%v]", strings.Join(p.messageCfg.Types, ", "))
	}
	return nil
}

// ValidateScope check if commit scope is valid.
func (p MessageProcessorImpl) ValidateScope(scope string) error {
	if len(p.messageCfg.Scope.Values) > 0 && !contains(scope, p.messageCfg.Scope.Values) {
		return fmt.Errorf("message scope should one of [%v]", strings.Join(p.messageCfg.Scope.Values, ", "))
	}
	return nil
}

// ValidateDescription check if commit description is valid.
func (p MessageProcessorImpl) ValidateDescription(description string) error {
	if !regexp.MustCompile("^[a-z]+.*$").MatchString(description) {
		return fmt.Errorf("description [%s] should begins with lowercase letter", description)
	}
	return nil
}

// Enhance add metadata on commit message.
func (p MessageProcessorImpl) Enhance(branch string, message string) (string, error) {
	if p.branchesCfg.DisableIssue || p.messageCfg.IssueFooterConfig().Key == "" || hasIssueID(message, p.messageCfg.IssueFooterConfig()) {
		return "", nil // enhance disabled
	}

	issue, err := p.IssueID(branch)
	if err != nil {
		return "", err
	}
	if issue == "" {
		return "", fmt.Errorf("could not find issue id using configured regex")
	}

	footer := formatIssueFooter(p.messageCfg.IssueFooterConfig(), issue)
	if !hasFooter(message) {
		return "\n" + footer, nil
	}

	return footer, nil
}

func formatIssueFooter(cfg CommitMessageFooterConfig, issue string) string {
	if !strings.HasPrefix(issue, cfg.AddValuePrefix) {
		issue = cfg.AddValuePrefix + issue
	}
	if cfg.UseHash {
		return fmt.Sprintf("%s #%s", cfg.Key, strings.TrimPrefix(issue, "#"))
	}
	return fmt.Sprintf("%s: %s", cfg.Key, issue)
}

// IssueID try to extract issue id from branch, return empty if not found.
func (p MessageProcessorImpl) IssueID(branch string) (string, error) {
	if p.branchesCfg.DisableIssue || p.messageCfg.Issue.Regex == "" {
		return "", nil
	}

	rstr := fmt.Sprintf("^%s(%s)%s$", p.branchesCfg.Prefix, p.messageCfg.Issue.Regex, p.branchesCfg.Suffix)
	r, err := regexp.Compile(rstr)
	if err != nil {
		return "", fmt.Errorf("could not compile issue regex: %s, error: %v", rstr, err.Error())
	}

	groups := r.FindStringSubmatch(branch)
	if len(groups) != 4 {
		return "", nil
	}
	return groups[2], nil
}

// Format a commit message returning header, body and footer.
func (p MessageProcessorImpl) Format(msg CommitMessage) (string, string, string) {
	var header strings.Builder
	header.WriteString(msg.Type)
	if msg.Scope != "" {
		header.WriteString("(" + msg.Scope + ")")
	}
	header.WriteString(": ")
	header.WriteString(msg.Description)

	var footer strings.Builder
	if msg.BreakingMessage() != "" {
		footer.WriteString(fmt.Sprintf("%s: %s", breakingChangeFooterKey, msg.BreakingMessage()))
	}
	if issue, exists := msg.Metadata[issueMetadataKey]; exists && p.messageCfg.IssueFooterConfig().Key != "" {
		if footer.Len() > 0 {
			footer.WriteString("\n")
		}
		footer.WriteString(formatIssueFooter(p.messageCfg.IssueFooterConfig(), issue))
	}

	return header.String(), msg.Body, footer.String()
}

// Parse a commit message.
func (p MessageProcessorImpl) Parse(subject, body string) CommitMessage {
	filteredSubject := subject
	if p.messageCfg.MessageSelector != "" {
		subjectRegex := regexp.MustCompile(p.messageCfg.MessageSelector)
		subjectMessageIndex := subjectRegex.SubexpIndex(messageRegexGroupName)
		subjectMatch := subjectRegex.FindStringSubmatch(subject)
		
		filteredSubject = subjectMatch[subjectMessageIndex]
	}
	
	commitType, scope, description, hasBreakingChange := parseSubjectMessage(filteredSubject)

	metadata := make(map[string]string)
	for key, mdCfg := range p.messageCfg.Footer {
		if mdCfg.Key != "" {
			prefixes := append([]string{mdCfg.Key}, mdCfg.KeySynonyms...)
			for _, prefix := range prefixes {
				if tagValue := extractFooterMetadata(prefix, body, mdCfg.UseHash); tagValue != "" {
					metadata[key] = tagValue
					break
				}
			}
		}
	}
	if tagValue := extractFooterMetadata(breakingChangeFooterKey, body, false); tagValue != "" {
		metadata[breakingChangeMetadataKey] = tagValue
		hasBreakingChange = true
	}

	return CommitMessage{
		Type:             commitType,
		Scope:            scope,
		Description:      description,
		Body:             body,
		IsBreakingChange: hasBreakingChange,
		Metadata:         metadata,
	}
}

func parseSubjectMessage(message string) (string, string, string, bool) {
	regex := regexp.MustCompile(`([a-z]+)(\((.*)\))?(!)?: (.*)`)
	result := regex.FindStringSubmatch(message)
	if len(result) != 6 {
		return "", "", message, false
	}
	return result[1], result[3], strings.TrimSpace(result[5]), result[4] == "!"
}

func extractFooterMetadata(key, text string, useHash bool) string {
	var regex *regexp.Regexp
	if useHash {
		regex = regexp.MustCompile(key + " (#.*)")
	} else {
		regex = regexp.MustCompile(key + ": (.*)")
	}

	result := regex.FindStringSubmatch(text)
	if len(result) < 2 {
		return ""
	}
	return result[1]
}

func hasFooter(message string) bool {
	r := regexp.MustCompile("^[a-zA-Z-]+: .*|^[a-zA-Z-]+ #.*|^" + breakingChangeFooterKey + ": .*")

	scanner := bufio.NewScanner(strings.NewReader(message))
	lines := 0
	for scanner.Scan() {
		if lines > 0 && r.MatchString(scanner.Text()) {
			return true
		}
		lines++
	}

	return false
}

func hasIssueID(message string, issueConfig CommitMessageFooterConfig) bool {
	var r *regexp.Regexp
	if issueConfig.UseHash {
		r = regexp.MustCompile(fmt.Sprintf("(?m)^%s #.+$", issueConfig.Key))
	} else {
		r = regexp.MustCompile(fmt.Sprintf("(?m)^%s: .+$", issueConfig.Key))
	}
	return r.MatchString(message)
}

func contains(value string, content []string) bool {
	for _, v := range content {
		if value == v {
			return true
		}
	}
	return false
}

func splitCommitMessageContent(content string) (string, string) {
	scanner := bufio.NewScanner(strings.NewReader(content))

	scanner.Scan()
	subject := scanner.Text()

	var body strings.Builder
	first := true
	for scanner.Scan() {
		if !first {
			body.WriteString("\n")
		}
		body.WriteString(scanner.Text())
		first = false
	}

	return subject, body.String()
}