package git

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"time"
)

// GitHubWebhook represents the GitHub pull request webhook payload
type GitHubWebhook struct {
	Action      string             `json:"action"`
	Number      int                `json:"number"`
	PullRequest *GitHubPullRequest `json:"pull_request"`
	Repository  *Repository        `json:"repository"`
	Sender      *User              `json:"sender"`
	Changes     *Changes           `json:"changes,omitempty"`
}

// GitHubPullRequest contains the pull request data from GitHub webhook
type GitHubPullRequest struct {
	ID                 int                `json:"id"`
	Number             int                `json:"number"`
	State              string             `json:"state"`
	Locked             bool               `json:"locked"`
	Title              string             `json:"title"`
	Body               string             `json:"body"`
	CreatedAt          time.Time          `json:"created_at"`
	UpdatedAt          time.Time          `json:"updated_at"`
	ClosedAt           *time.Time         `json:"closed_at"`
	MergedAt           *time.Time         `json:"merged_at"`
	MergeCommitSHA     *string            `json:"merge_commit_sha"`
	Assignee           *User              `json:"assignee"`
	Assignees          []*User            `json:"assignees"`
	RequestedReviewers []*User            `json:"requested_reviewers"`
	Labels             []*Label           `json:"labels"`
	Milestone          *Milestone         `json:"milestone"`
	Draft              bool               `json:"draft"`
	Merged             bool               `json:"merged"`
	Mergeable          *bool              `json:"mergeable"`
	MergeableState     string             `json:"mergeable_state"`
	MergedBy           *User              `json:"merged_by"`
	Comments           int                `json:"comments"`
	ReviewComments     int                `json:"review_comments"`
	Commits            int                `json:"commits"`
	Additions          int                `json:"additions"`
	Deletions          int                `json:"deletions"`
	ChangedFiles       int                `json:"changed_files"`
	Head               *PullRequestBranch `json:"head"`
	Base               *PullRequestBranch `json:"base"`
	User               *User              `json:"user"`
}

// PullRequestBranch contains branch information
type PullRequestBranch struct {
	Label string      `json:"label"`
	Ref   string      `json:"ref"`
	SHA   string      `json:"sha"`
	User  *User       `json:"user"`
	Repo  *Repository `json:"repo"`
}

// Repository contains repository information
type Repository struct {
	ID                        int                  `json:"id"`
	NodeID                    string               `json:"node_id"`
	Name                      string               `json:"name"`
	FullName                  string               `json:"full_name"`
	Private                   bool                 `json:"private"`
	Owner                     *User                `json:"owner"`
	Description               *string              `json:"description"`
	Fork                      bool                 `json:"fork"`
	CreatedAt                 time.Time            `json:"created_at"`
	UpdatedAt                 time.Time            `json:"updated_at"`
	PushedAt                  time.Time            `json:"pushed_at"`
	GitURL                    string               `json:"git_url"`
	SSHURL                    string               `json:"ssh_url"`
	CloneURL                  string               `json:"clone_url"`
	SvnURL                    string               `json:"svn_url"`
	Homepage                  *string              `json:"homepage"`
	Size                      int                  `json:"size"`
	StargazersCount           int                  `json:"stargazers_count"`
	WatchersCount             int                  `json:"watchers_count"`
	Language                  *string              `json:"language"`
	HasIssues                 bool                 `json:"has_issues"`
	HasProjects               bool                 `json:"has_projects"`
	HasDownloads              bool                 `json:"has_downloads"`
	HasWiki                   bool                 `json:"has_wiki"`
	HasPages                  bool                 `json:"has_pages"`
	HasDiscussions            bool                 `json:"has_discussions"`
	ForksCount                int                  `json:"forks_count"`
	Archived                  bool                 `json:"archived"`
	Disabled                  bool                 `json:"disabled"`
	License                   *License             `json:"license"`
	AllowForking              bool                 `json:"allow_forking"`
	IsTemplate                bool                 `json:"is_template"`
	WebCommitSignoffRequired  bool                 `json:"web_commit_signoff_required"`
	Topics                    []string             `json:"topics"`
	Visibility                string               `json:"visibility"`
	DefaultBranch             string               `json:"default_branch"`
	AllowSquashMerge          bool                 `json:"allow_squash_merge"`
	AllowMergeCommit          bool                 `json:"allow_merge_commit"`
	AllowRebaseMerge          bool                 `json:"allow_rebase_merge"`
	AllowAutoMerge            bool                 `json:"allow_auto_merge"`
	DeleteBranchOnMerge       bool                 `json:"delete_branch_on_merge"`
	AllowUpdateBranch         bool                 `json:"allow_update_branch"`
	UseSquashPrTitleAsDefault bool                 `json:"use_squash_pr_title_as_default"`
	SquashMergeCommitMessage  string               `json:"squash_merge_commit_message"`
	SquashMergeCommitTitle    string               `json:"squash_merge_commit_title"`
	MergeCommitMessage        string               `json:"merge_commit_message"`
	MergeCommitTitle          string               `json:"merge_commit_title"`
	SecurityAndAnalysis       *SecurityAndAnalysis `json:"security_and_analysis"`
}

// User contains user information
type User struct {
	Login                   string     `json:"login"`
	ID                      int        `json:"id"`
	NodeID                  string     `json:"node_id"`
	AvatarURL               string     `json:"avatar_url"`
	GravatarID              string     `json:"gravatar_id"`
	URL                     string     `json:"url"`
	HTMLURL                 string     `json:"html_url"`
	FollowersURL            string     `json:"followers_url"`
	FollowingURL            string     `json:"following_url"`
	GistsURL                string     `json:"gists_url"`
	StarredURL              string     `json:"starred_url"`
	SubscriptionsURL        string     `json:"subscriptions_url"`
	OrganizationsURL        string     `json:"organizations_url"`
	ReposURL                string     `json:"repos_url"`
	EventsURL               string     `json:"events_url"`
	ReceivedEventsURL       string     `json:"received_events_url"`
	Type                    string     `json:"type"`
	SiteAdmin               bool       `json:"site_admin"`
	Name                    *string    `json:"name"`
	Company                 *string    `json:"company"`
	Blog                    *string    `json:"blog"`
	Location                *string    `json:"location"`
	Email                   *string    `json:"email"`
	Hireable                *bool      `json:"hireable"`
	Bio                     *string    `json:"bio"`
	TwitterUsername         *string    `json:"twitter_username"`
	PublicRepos             int        `json:"public_repos"`
	PublicGists             int        `json:"public_gists"`
	Followers               int        `json:"followers"`
	Following               int        `json:"following"`
	CreatedAt               time.Time  `json:"created_at"`
	UpdatedAt               time.Time  `json:"updated_at"`
	PrivateGists            int        `json:"private_gists"`
	TotalPrivateRepos       int        `json:"total_private_repos"`
	OwnedPrivateRepos       int        `json:"owned_private_repos"`
	DiskUsage               int        `json:"disk_usage"`
	Collaborators           int        `json:"collaborators"`
	TwoFactorAuthentication bool       `json:"two_factor_authentication"`
	Plan                    *Plan      `json:"plan"`
	SuspendedAt             *time.Time `json:"suspended_at"`
	BusinessPlus            bool       `json:"business_plus"`
	LdapDn                  *string    `json:"ldap_dn"`
}

// Label contains label information
type Label struct {
	ID          int     `json:"id"`
	NodeID      string  `json:"node_id"`
	URL         string  `json:"url"`
	Name        string  `json:"name"`
	Description *string `json:"description"`
	Color       string  `json:"color"`
	Default     bool    `json:"default"`
}

// Milestone contains milestone information
type Milestone struct {
	URL          string     `json:"url"`
	HTMLURL      string     `json:"html_url"`
	LabelsURL    string     `json:"labels_url"`
	ID           int        `json:"id"`
	NodeID       string     `json:"node_id"`
	Number       int        `json:"number"`
	State        string     `json:"state"`
	Title        string     `json:"title"`
	Description  *string    `json:"description"`
	Creator      *User      `json:"creator"`
	OpenIssues   int        `json:"open_issues"`
	ClosedIssues int        `json:"closed_issues"`
	CreatedAt    time.Time  `json:"created_at"`
	UpdatedAt    time.Time  `json:"updated_at"`
	DueOn        *time.Time `json:"due_on"`
	ClosedAt     *time.Time `json:"closed_at"`
}

// License contains license information
type License struct {
	Key     string `json:"key"`
	Name    string `json:"name"`
	URL     string `json:"url"`
	SpdxID  string `json:"spdx_id"`
	NodeID  string `json:"node_id"`
	HTMLURL string `json:"html_url"`
}

// SecurityAndAnalysis contains security and analysis information
type SecurityAndAnalysis struct {
	AdvancedSecurity             *SecurityFeature `json:"advanced_security"`
	SecretScanning               *SecurityFeature `json:"secret_scanning"`
	SecretScanningPushProtection *SecurityFeature `json:"secret_scanning_push_protection"`
	DependabotSecurityUpdates    *SecurityFeature `json:"dependabot_security_updates"`
	DependencyGraph              *SecurityFeature `json:"dependency_graph"`
}

// SecurityFeature contains security feature information
type SecurityFeature struct {
	Status string `json:"status"`
}

// Plan contains plan information
type Plan struct {
	Name          string `json:"name"`
	Space         int    `json:"space"`
	Collaborators int    `json:"collaborators"`
	PrivateRepos  int    `json:"private_repos"`
}

// Changes contains information about what changed in the webhook
type Changes struct {
	Title *Change `json:"title,omitempty"`
	Body  *Change `json:"body,omitempty"`
	Base  *Change `json:"base,omitempty"`
}

// Change contains information about a specific change
type Change struct {
	From string `json:"from"`
}

// ValidateSignature validates GitHub webhook signature using SHA-256 HMAC
func ValidateSignature(payload []byte, signature, secret string) error {
	if secret == "" {
		return errors.New("webhook secret not configured")
	}

	if !strings.HasPrefix(signature, "sha256=") {
		return errors.New("signature must use sha256")
	}

	expectedMAC, err := hex.DecodeString(signature[7:])
	if err != nil {
		return fmt.Errorf("invalid signature format: %w", err)
	}

	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(payload)
	computedMAC := mac.Sum(nil)

	if !hmac.Equal(expectedMAC, computedMAC) {
		return errors.New("signature verification failed")
	}

	return nil
}

// ParseWebhook parses GitHub webhook payload
func ParseWebhook(payload []byte) (*GitHubWebhook, error) {
	var webhook GitHubWebhook
	if err := json.Unmarshal(payload, &webhook); err != nil {
		return nil, fmt.Errorf("failed to parse webhook: %w", err)
	}
	return &webhook, nil
}

// IsValidMergeEvent checks if webhook represents a merged PR
func IsValidMergeEvent(webhook *GitHubWebhook) bool {
	return webhook.Action == "closed" &&
		webhook.PullRequest != nil &&
		webhook.PullRequest.Merged &&
		webhook.PullRequest.Head != nil
}

// ExtractTaskID extracts task ID from branch name like "solution/[task-id]-title" or "subtasks/[task-id]-title"
func ExtractTaskID(branchName string) (string, error) {
	// Match patterns like "solution/(task-123)-title", "subtasks/(task-456)-description", etc.
	re := regexp.MustCompile(`^(?:solution|subtasks)/\(([^)]+)\)-.+$`)
	matches := re.FindStringSubmatch(branchName)

	if len(matches) != 2 {
		return "", fmt.Errorf("branch name '%s' does not match expected pattern (solution/(task-id)-title or subtasks/(task-id)-title)", branchName)
	}

	return matches[1], nil
}

// ProcessMergeWebhook processes a GitHub PR merge webhook and returns the task ID
// This function handles the complete GitHub webhook payload structure
func ProcessMergeWebhook(payload []byte, signature, secret string) (string, error) {
	// Validate signature
	if err := ValidateSignature(payload, signature, secret); err != nil {
		return "", fmt.Errorf("signature validation failed: %w", err)
	}

	// Parse webhook
	webhook, err := ParseWebhook(payload)
	if err != nil {
		return "", fmt.Errorf("webhook parsing failed: %w", err)
	}

	// Check if it's a merge event
	if !IsValidMergeEvent(webhook) {
		return "", errors.New("not a valid merge event")
	}

	// Extract task ID from branch name
	taskID, err := ExtractTaskID(webhook.PullRequest.Head.Ref)
	if err != nil {
		return "", fmt.Errorf("task ID extraction failed: %w", err)
	}

	return taskID, nil
}

// GetWebhookInfo returns comprehensive information about the webhook for debugging/logging
func GetWebhookInfo(webhook *GitHubWebhook) map[string]interface{} {
	info := map[string]interface{}{
		"action": webhook.Action,
		"number": webhook.Number,
	}

	if webhook.PullRequest != nil {
		info["pr_id"] = webhook.PullRequest.ID
		info["pr_title"] = webhook.PullRequest.Title
		info["pr_state"] = webhook.PullRequest.State
		info["pr_merged"] = webhook.PullRequest.Merged
		info["pr_merged_at"] = webhook.PullRequest.MergedAt
		info["pr_merged_by"] = webhook.PullRequest.MergedBy

		if webhook.PullRequest.Head != nil {
			info["head_ref"] = webhook.PullRequest.Head.Ref
			info["head_sha"] = webhook.PullRequest.Head.SHA
		}

		if webhook.PullRequest.Base != nil {
			info["base_ref"] = webhook.PullRequest.Base.Ref
			info["base_sha"] = webhook.PullRequest.Base.SHA
		}
	}

	if webhook.Repository != nil {
		info["repo_name"] = webhook.Repository.Name
		info["repo_full_name"] = webhook.Repository.FullName
	}

	if webhook.Sender != nil {
		info["sender_login"] = webhook.Sender.Login
		info["sender_id"] = webhook.Sender.ID
	}

	return info
}