package webhook

import "encoding/json"

// GiteaPushPayload represents a Gitea push webhook payload.
//
//nolint:tagliatelle // Field names match Gitea API (snake_case)
type GiteaPushPayload struct {
	Ref        string      `json:"ref"`
	Before     string      `json:"before"`
	After      string      `json:"after"`
	CompareURL UnparsedURL `json:"compare_url"`
	Repository struct {
		FullName string      `json:"full_name"`
		CloneURL UnparsedURL `json:"clone_url"`
		SSHURL   string      `json:"ssh_url"`
		HTMLURL  UnparsedURL `json:"html_url"`
	} `json:"repository"`
	Pusher struct {
		Username string `json:"username"`
		Email    string `json:"email"`
	} `json:"pusher"`
	Commits []struct {
		ID      string      `json:"id"`
		URL     UnparsedURL `json:"url"`
		Message string      `json:"message"`
		Author  struct {
			Name  string `json:"name"`
			Email string `json:"email"`
		} `json:"author"`
	} `json:"commits"`
}

// GitHubPushPayload represents a GitHub push webhook payload.
//
//nolint:tagliatelle // Field names match GitHub API (snake_case)
type GitHubPushPayload struct {
	Ref        string `json:"ref"`
	Before     string `json:"before"`
	After      string `json:"after"`
	CompareURL string `json:"compare"`
	Repository struct {
		FullName string      `json:"full_name"`
		CloneURL UnparsedURL `json:"clone_url"`
		SSHURL   string      `json:"ssh_url"`
		HTMLURL  UnparsedURL `json:"html_url"`
	} `json:"repository"`
	Pusher struct {
		Name  string `json:"name"`
		Email string `json:"email"`
	} `json:"pusher"`
	HeadCommit *struct {
		ID      string      `json:"id"`
		URL     UnparsedURL `json:"url"`
		Message string      `json:"message"`
	} `json:"head_commit"`
	Commits []struct {
		ID      string      `json:"id"`
		URL     UnparsedURL `json:"url"`
		Message string      `json:"message"`
		Author  struct {
			Name  string `json:"name"`
			Email string `json:"email"`
		} `json:"author"`
	} `json:"commits"`
}

// GitLabPushPayload represents a GitLab push webhook payload.
//
//nolint:tagliatelle // Field names match GitLab API (snake_case)
type GitLabPushPayload struct {
	Ref       string `json:"ref"`
	Before    string `json:"before"`
	After     string `json:"after"`
	UserName  string `json:"user_name"`
	UserEmail string `json:"user_email"`
	Project   struct {
		PathWithNamespace string      `json:"path_with_namespace"`
		GitHTTPURL        UnparsedURL `json:"git_http_url"`
		GitSSHURL         string      `json:"git_ssh_url"`
		WebURL            UnparsedURL `json:"web_url"`
	} `json:"project"`
	Commits []struct {
		ID      string      `json:"id"`
		URL     UnparsedURL `json:"url"`
		Message string      `json:"message"`
		Author  struct {
			Name  string `json:"name"`
			Email string `json:"email"`
		} `json:"author"`
	} `json:"commits"`
}

// ParsePushPayload parses a raw webhook payload into a normalized PushEvent
// based on the detected webhook source. Returns an error if JSON unmarshaling
// fails. For SourceUnknown, falls back to Gitea format for backward
// compatibility.
func ParsePushPayload(source Source, payload []byte) (*PushEvent, error) {
	switch source {
	case SourceGitHub:
		return parseGitHubPush(payload)
	case SourceGitLab:
		return parseGitLabPush(payload)
	case SourceGitea, SourceUnknown:
		// Gitea and unknown both use Gitea format for backward compatibility.
		return parseGiteaPush(payload)
	}

	// Unreachable for known source values, but satisfies exhaustive checker.
	return parseGiteaPush(payload)
}

func parseGiteaPush(payload []byte) (*PushEvent, error) {
	var p GiteaPushPayload

	unmarshalErr := json.Unmarshal(payload, &p)
	if unmarshalErr != nil {
		return nil, unmarshalErr
	}

	commitURL := extractGiteaCommitURL(p)

	return &PushEvent{
		Source:    SourceGitea,
		Ref:       p.Ref,
		Before:    p.Before,
		After:     p.After,
		Branch:    extractBranch(p.Ref),
		RepoName:  p.Repository.FullName,
		CloneURL:  p.Repository.CloneURL,
		HTMLURL:   p.Repository.HTMLURL,
		CommitURL: commitURL,
		Pusher:    p.Pusher.Username,
	}, nil
}

func parseGitHubPush(payload []byte) (*PushEvent, error) {
	var p GitHubPushPayload

	unmarshalErr := json.Unmarshal(payload, &p)
	if unmarshalErr != nil {
		return nil, unmarshalErr
	}

	commitURL := extractGitHubCommitURL(p)

	return &PushEvent{
		Source:    SourceGitHub,
		Ref:       p.Ref,
		Before:    p.Before,
		After:     p.After,
		Branch:    extractBranch(p.Ref),
		RepoName:  p.Repository.FullName,
		CloneURL:  p.Repository.CloneURL,
		HTMLURL:   p.Repository.HTMLURL,
		CommitURL: commitURL,
		Pusher:    p.Pusher.Name,
	}, nil
}

func parseGitLabPush(payload []byte) (*PushEvent, error) {
	var p GitLabPushPayload

	unmarshalErr := json.Unmarshal(payload, &p)
	if unmarshalErr != nil {
		return nil, unmarshalErr
	}

	commitURL := extractGitLabCommitURL(p)

	return &PushEvent{
		Source:    SourceGitLab,
		Ref:       p.Ref,
		Before:    p.Before,
		After:     p.After,
		Branch:    extractBranch(p.Ref),
		RepoName:  p.Project.PathWithNamespace,
		CloneURL:  p.Project.GitHTTPURL,
		HTMLURL:   p.Project.WebURL,
		CommitURL: commitURL,
		Pusher:    p.UserName,
	}, nil
}

// extractBranch extracts the branch name from a git ref.
func extractBranch(ref string) string {
	// refs/heads/main -> main
	const prefix = "refs/heads/"

	if len(ref) >= len(prefix) && ref[:len(prefix)] == prefix {
		return ref[len(prefix):]
	}

	return ref
}

// extractGiteaCommitURL extracts the commit URL from a Gitea push payload.
// Prefers the URL from the head commit, falls back to constructing from repo URL.
func extractGiteaCommitURL(payload GiteaPushPayload) UnparsedURL {
	for _, commit := range payload.Commits {
		if commit.ID == payload.After && commit.URL != "" {
			return commit.URL
		}
	}

	if payload.Repository.HTMLURL != "" && payload.After != "" {
		return UnparsedURL(payload.Repository.HTMLURL.String() + "/commit/" + payload.After)
	}

	return ""
}

// extractGitHubCommitURL extracts the commit URL from a GitHub push payload.
// Prefers head_commit.url, then searches commits, then constructs from repo URL.
func extractGitHubCommitURL(payload GitHubPushPayload) UnparsedURL {
	if payload.HeadCommit != nil && payload.HeadCommit.URL != "" {
		return payload.HeadCommit.URL
	}

	for _, commit := range payload.Commits {
		if commit.ID == payload.After && commit.URL != "" {
			return commit.URL
		}
	}

	if payload.Repository.HTMLURL != "" && payload.After != "" {
		return UnparsedURL(payload.Repository.HTMLURL.String() + "/commit/" + payload.After)
	}

	return ""
}

// extractGitLabCommitURL extracts the commit URL from a GitLab push payload.
// Prefers commit URL from the commits list, falls back to constructing from
// project web URL.
func extractGitLabCommitURL(payload GitLabPushPayload) UnparsedURL {
	for _, commit := range payload.Commits {
		if commit.ID == payload.After && commit.URL != "" {
			return commit.URL
		}
	}

	if payload.Project.WebURL != "" && payload.After != "" {
		return UnparsedURL(payload.Project.WebURL.String() + "/-/commit/" + payload.After)
	}

	return ""
}