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 parsePush(payload, githubPushEvent)
	case SourceGitLab:
		return parsePush(payload, gitlabPushEvent)
	case SourceGitea, SourceUnknown:
		// Gitea and unknown both use Gitea format for backward compatibility.
		return parsePush(payload, giteaPushEvent)
	}

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

// parsePush unmarshals payload into P and converts it into a normalized
// PushEvent via build.
func parsePush[P any](payload []byte, build func(P) *PushEvent) (*PushEvent, error) {
	var p P

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

	return build(p), nil
}

// basePushEvent builds a PushEvent populated with the fields shared by all
// webhook sources.
func basePushEvent(source Source, ref, before, after string) *PushEvent {
	return &PushEvent{
		Source: source,
		Ref:    ref,
		Before: before,
		After:  after,
		Branch: extractBranch(ref),
	}
}

// giteaPushEvent converts a Gitea push payload to a normalized PushEvent.
func giteaPushEvent(p GiteaPushPayload) *PushEvent {
	event := basePushEvent(SourceGitea, p.Ref, p.Before, p.After)
	event.RepoName = p.Repository.FullName
	event.CloneURL = p.Repository.CloneURL
	event.HTMLURL = p.Repository.HTMLURL
	event.CommitURL = extractGiteaCommitURL(p)
	event.Pusher = p.Pusher.Username

	return event
}

// gitlabPushEvent converts a GitLab push payload to a normalized PushEvent.
func gitlabPushEvent(p GitLabPushPayload) *PushEvent {
	event := basePushEvent(SourceGitLab, p.Ref, p.Before, p.After)
	event.RepoName = p.Project.PathWithNamespace
	event.CloneURL = p.Project.GitHTTPURL
	event.HTMLURL = p.Project.WebURL
	event.CommitURL = extractGitLabCommitURL(p)
	event.Pusher = p.UserName

	return event
}

// githubPushEvent converts a GitHub push payload to a normalized PushEvent.
func githubPushEvent(p GitHubPushPayload) *PushEvent {
	event := basePushEvent(SourceGitHub, p.Ref, p.Before, p.After)
	event.RepoName = p.Repository.FullName
	event.CloneURL = p.Repository.CloneURL
	event.HTMLURL = p.Repository.HTMLURL
	event.CommitURL = extractGitHubCommitURL(p)
	event.Pusher = p.Pusher.Name

	return event
}

// 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 ""
}