import crypto from 'crypto';
import { ComposeService } from './ComposeService';
import { StackOpLockService, stackOpSkipMessage, type StackOpAction } from './StackOpLockService';
import { DatabaseService, type Webhook } from './DatabaseService';
import { FileSystemService } from './FileSystemService';
import { GitSourceService } from './GitSourceService';
import { HealthGateService } from './HealthGateService';
import { LicenseService } from './LicenseService';
import { PROXY_TIER_HEADER } from './license-headers';
import { NodeRegistry } from './NodeRegistry';
import { getErrorMessage } from '../utils/errors';
import { redactSensitiveText } from '../utils/safeLog';
import { isValidStackName } from '../utils/validation';
import { assertPolicyGateAllows, buildSystemPolicyGateOptions } from '../helpers/policyGate';

type ExecutionResult = { success: boolean; error?: string; duration_ms: number };
type ExecutionStatus = 'success' | 'failure';

const REMOTE_WEBHOOK_REQUEST_TIMEOUT_MS = 30_000;

// Maps a webhook lifecycle action to the per-stack lock action. 'pull' updates,
// so it locks as 'update'; 'git-pull' is excluded (it locks inside GitSourceService).
const WEBHOOK_LOCK_ACTION: Record<string, StackOpAction | undefined> = {
    deploy: 'deploy',
    restart: 'restart',
    stop: 'stop',
    start: 'start',
    pull: 'update',
};

export class WebhookService {
    private static instance: WebhookService;
    // Stable per-process decoy secret used to keep HMAC work non-skippable on
    // reject paths (unknown webhook id, disabled, etc.). Never accepts a
    // signature: the trigger handler decides the final 202 / 404 outcome from
    // independent conditions and only consults the HMAC result when every
    // other check has already passed.
    private static decoySecret: string | null = null;

    public static getInstance(): WebhookService {
        if (!WebhookService.instance) {
            WebhookService.instance = new WebhookService();
        }
        return WebhookService.instance;
    }

    public static getDecoySecret(): string {
        if (!WebhookService.decoySecret) {
            WebhookService.decoySecret = crypto.randomBytes(32).toString('hex');
        }
        return WebhookService.decoySecret;
    }

    public generateSecret(): string {
        return crypto.randomBytes(32).toString('hex');
    }

    public validateSignature(payload: string, secret: string, signature: string): boolean {
        // Always perform HMAC and timingSafeEqual against a fixed-length
        // buffer so the wall-clock cost of this call is independent of the
        // shape of the input signature. Without this, the early-return paths
        // (missing header, wrong prefix, malformed hex) would skip the HMAC
        // and let an attacker distinguish those cases from a real-shape
        // wrong-secret case through repeated near-rate-limit probes with a
        // large attacker-controlled body. Timing now depends only on the
        // size of `payload`, which the attacker already controls and which
        // does not reveal anything about the webhook id.
        const expected = crypto.createHmac('sha256', secret).update(payload).digest();
        const provided = Buffer.alloc(32);
        let formatOk = false;

        const parts = signature.split('=');
        if (parts.length === 2 && parts[0] === 'sha256' && /^[0-9a-fA-F]{64}$/.test(parts[1])) {
            provided.write(parts[1], 'hex');
            formatOk = true;
        }

        const sigEq = crypto.timingSafeEqual(expected, provided);
        return formatOk && sigEq;
    }

    public async gitSourceExists(stackName: string, nodeId: number): Promise<boolean> {
        const node = NodeRegistry.getInstance().getNode(nodeId);
        if (!node) return false;
        if (node.type !== 'remote') return GitSourceService.getInstance().get(stackName) !== undefined;

        const response = await this.remoteStackRequest(nodeId, stackName, 'git-source', 'GET');
        return response.ok;
    }

    public async execute(
        webhook: Webhook,
        action: string,
        triggerSource: string | null,
        atomic?: boolean,
    ): Promise<ExecutionResult> {
        if (webhook.id === undefined) {
            throw new Error('Webhook must be loaded from the database before execution');
        }
        const webhookId = webhook.id;

        const nodeId = webhook.node_id || NodeRegistry.getInstance().getDefaultNodeId();
        const node = NodeRegistry.getInstance().getNode(nodeId);
        if (!node) {
            const error = `Node for webhook "${webhook.name}" was not found`;
            this.recordExecution(webhookId, action, 'failure', triggerSource, 0, error);
            return { success: false, error, duration_ms: 0 };
        }

        if (node.type === 'remote') {
            return this.executeRemote(webhookId, nodeId, webhook.stack_name, action, triggerSource, atomic);
        }

        return this.executeLocal(webhookId, nodeId, webhook.stack_name, action, triggerSource, atomic);
    }

    public maskSecret(secret: string): string {
        if (secret.length <= 8) return '********';
        return '********' + secret.slice(-4);
    }

    private async executeLocal(
        webhookId: number,
        nodeId: number,
        stackName: string,
        action: string,
        triggerSource: string | null,
        atomic?: boolean,
    ): Promise<ExecutionResult> {
        const stacks = await FileSystemService.getInstance(nodeId).getStacks();
        if (!stacks.includes(stackName)) {
            const error = `Stack "${stackName}" not found`;
            this.recordExecution(webhookId, action, 'failure', triggerSource, 0, error);
            return { success: false, error, duration_ms: 0 };
        }

        const startTime = Date.now();
        try {
            // git-pull pulls then deploys through GitSourceService, which holds
            // the per-stack lock itself; locking here too would self-conflict.
            if (action === 'git-pull') {
                return this.executeLocalGitPull(webhookId, stackName, action, triggerSource, startTime);
            }
            const lockAction = WEBHOOK_LOCK_ACTION[action];
            if (!lockAction) throw new Error(`Unknown action: ${action}`);
            const compose = ComposeService.getInstance(nodeId);
            // Run the lifecycle op under the per-stack lock so a webhook cannot
            // race a manual deploy/update/rollback/backup on the same stack.
            const lock = await StackOpLockService.getInstance().runExclusive(
                nodeId, stackName, lockAction, 'system',
                async () => {
                    switch (action) {
                        case 'deploy':
                            await assertPolicyGateAllows(
                                stackName,
                                nodeId,
                                buildSystemPolicyGateOptions('webhook', { auditPath: `/api/webhooks/${webhookId}/execute` }),
                            );
                            await compose.deployStack(stackName, undefined, atomic);
                            HealthGateService.getInstance().begin(nodeId, stackName, 'deploy', 'system:webhook');
                            break;
                        case 'restart':
                            await compose.runCommand(stackName, 'restart');
                            break;
                        case 'stop':
                            await compose.runCommand(stackName, 'stop');
                            break;
                        case 'start':
                            await compose.runCommand(stackName, 'start');
                            break;
                        case 'pull':
                            await assertPolicyGateAllows(
                                stackName,
                                nodeId,
                                buildSystemPolicyGateOptions('webhook', { auditPath: `/api/webhooks/${webhookId}/execute` }),
                            );
                            await compose.updateStack(stackName, undefined, atomic);
                            HealthGateService.getInstance().begin(nodeId, stackName, 'update', 'system:webhook');
                            break;
                    }
                },
            );

            const durationMs = Date.now() - startTime;
            if (!lock.ran) {
                const error = stackOpSkipMessage(stackName, lock.existing.action);
                this.recordExecution(webhookId, action, 'failure', triggerSource, durationMs, error);
                return { success: false, error, duration_ms: durationMs };
            }
            this.recordExecution(webhookId, action, 'success', triggerSource, durationMs, null);
            return { success: true, duration_ms: durationMs };
        } catch (err) {
            const durationMs = Date.now() - startTime;
            const error = getErrorMessage(err, 'Unknown error');
            this.recordExecution(webhookId, action, 'failure', triggerSource, durationMs, error);
            return { success: false, error, duration_ms: durationMs };
        }
    }

    private async executeLocalGitPull(
        webhookId: number,
        stackName: string,
        action: string,
        triggerSource: string | null,
        startTime: number,
    ): Promise<ExecutionResult> {
        const result = await GitSourceService.getInstance().handleWebhookPull(stackName);
        const durationMs = Date.now() - startTime;
        if (result.status === 'error') {
            this.recordExecution(webhookId, action, 'failure', triggerSource, durationMs, result.message);
            return { success: false, error: result.message, duration_ms: durationMs };
        }

        const skipped = result.status === 'skipped';
        // A debounced pull is rate-limited, not failed (the route answers 202
        // Accepted). Record it as a success carrying the debounce note so it
        // does not pollute the webhook's failure history.
        this.recordExecution(
            webhookId,
            action,
            'success',
            triggerSource,
            durationMs,
            skipped ? result.message : null,
        );
        return { success: true, error: undefined, duration_ms: durationMs };
    }

    private async executeRemote(
        webhookId: number,
        nodeId: number,
        stackName: string,
        action: string,
        triggerSource: string | null,
        atomic?: boolean,
    ): Promise<ExecutionResult> {
        const startTime = Date.now();
        try {
            const endpoint = action === 'git-pull'
                ? 'git-source/webhook-pull'
                : action === 'pull'
                    ? 'update'
                    : action;
            const body = atomic === undefined ? undefined : { atomic };
            const response = await this.remoteStackRequest(nodeId, stackName, endpoint, 'POST', body);
            const durationMs = Date.now() - startTime;
            const payload = await response.json().catch(() => ({})) as { error?: string; message?: string; status?: string };

            if (!response.ok || payload.status === 'error') {
                const error = payload.error || payload.message || `Remote ${action} failed with status ${response.status}`;
                this.recordExecution(webhookId, action, 'failure', triggerSource, durationMs, error);
                return { success: false, error, duration_ms: durationMs };
            }

            // A debounced remote pull comes back 202 with status "skipped": it was
            // accepted and rate-limited, not failed. Record it as a success with
            // the debounce note rather than failure noise.
            const skipped = payload.status === 'skipped';
            this.recordExecution(webhookId, action, 'success', triggerSource, durationMs, skipped ? (payload.message ?? null) : null);
            return { success: true, duration_ms: durationMs };
        } catch (err) {
            const durationMs = Date.now() - startTime;
            const error = getErrorMessage(err, 'Remote node operation failed');
            this.recordExecution(webhookId, action, 'failure', triggerSource, durationMs, error);
            return { success: false, error, duration_ms: durationMs };
        }
    }

    private async remoteStackRequest(
        nodeId: number,
        stackName: string,
        endpoint: string,
        method: 'GET' | 'POST',
        body?: unknown,
    ): Promise<Response> {
        const target = NodeRegistry.getInstance().getProxyTarget(nodeId);
        if (!target) throw new Error('Remote node is unreachable or not configured');

        const headers: Record<string, string> = { 'Content-Type': 'application/json' };
        if (target.apiToken) headers.Authorization = `Bearer ${target.apiToken}`;

        const licenseHeaders = LicenseService.getInstance().getProxyHeaders();
        headers[PROXY_TIER_HEADER] = licenseHeaders.tier;

        const controller = new AbortController();
        const timer = setTimeout(() => controller.abort(), REMOTE_WEBHOOK_REQUEST_TIMEOUT_MS);
        try {
            // nodeId selects a server-controlled entry from the registry
            // (CodeQL GOOD pattern: user input maps to known values, not concatenated into the URL).
            const targetBase = new URL(target.apiUrl);
            const protocol = targetBase.protocol;
            const host = targetBase.host;
            const hostname = targetBase.hostname;

            // Verify the hostname is in the configured-node allow-list.
            const allowedHosts = DatabaseService.getInstance().getNodes()
                .filter(n => n.api_url)
                .map(n => new URL(n.api_url!).hostname);
            if (!allowedHosts.includes(hostname)) {
                throw new Error('Remote node hostname is not a configured node');
            }

            // Restrict protocol to http/https (prevents file://, ftp://, etc.).
            if (protocol !== 'http:' && protocol !== 'https:') {
                throw new Error('Remote node URL must use http:// or https://');
            }

            // Validate path components to prevent traversal.
            if (!isValidStackName(stackName)) {
                throw new Error('Invalid stack name');
            }
            if (!/^[a-z][a-z0-9/-]*$/.test(endpoint) || endpoint.includes('..')) {
                throw new Error('Invalid endpoint');
            }

            // Build URL from validated, server-controlled components.
            const url = `${protocol}//${host}/api/stacks/${encodeURIComponent(stackName)}/${endpoint}`;
            return await fetch(url, {
                method,
                headers,
                body: method === 'GET' || body === undefined ? undefined : JSON.stringify(body),
                signal: controller.signal,
            });
        } catch (err) {
            if (controller.signal.aborted) {
                throw new Error('Remote node request timed out', { cause: err });
            }
            throw err;
        } finally {
            clearTimeout(timer);
        }
    }

    private recordExecution(
        webhookId: number,
        action: string,
        status: ExecutionStatus,
        triggerSource: string | null,
        durationMs: number,
        error: string | null,
    ): void {
        // Execution history is readable in the UI; scrub bearer tokens,
        // JWTs, URL credentials, and homedir paths before persisting so a
        // compose / remote-node error surfacing on the dashboard cannot leak
        // operator secrets or infrastructure details.
        const safeError = error === null ? null : redactSensitiveText(error);
        try {
            DatabaseService.getInstance().addWebhookExecution({
                webhook_id: webhookId,
                action,
                status,
                trigger_source: triggerSource,
                duration_ms: durationMs,
                error: safeError,
                executed_at: Date.now(),
            });
        } catch (err) {
            // The webhook_executions table has ON DELETE CASCADE on webhook_id,
            // so a delete that races an in-flight execution removes the parent
            // row and any insert here fails the FK constraint. Swallow that
            // race: the trigger already returned 202 and the action either
            // ran or failed before reaching this point. Other write errors
            // are still worth logging as warnings so a structural problem
            // does not go silent.
            console.warn(
                `[Webhooks] Could not record execution for webhook ${webhookId} ` +
                `(parent webhook may have been deleted mid-flight): ${getErrorMessage(err, 'Unknown error')}`,
            );
        }
    }
}