import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
import { dirname, join } from 'path';
import { PlatformGraphqlService } from '../platform/platform-graphql.service';
import {
    DEFAULT_SETUP_STATE,
    SETUP_STEP_NAMES,
    type SetupState,
    type SetupStepName,
} from './setup-state.defaults';

const SETUP_STATE_PATH = join(process.cwd(), 'data', 'setup-state.json');

// File-backed store for the onboarding wizard's progress. Mirrors the
// pattern of ThemeService and WidgetConfigService — load on init, cache in
// memory, write on every change. No backups (the data is small and easily
// recreated by the wizard if it ever gets corrupted).
//
// Workspace scoping: the sidecar's API key is scoped to exactly one
// workspace, so on first access we compare the file's stored workspaceId
// against the live currentWorkspace.id from the platform. If they differ
// (DB reset, re-onboard, sidecar pointed at a new workspace), the file is
// reset before any reads return. This guarantees a fresh wizard for a
// fresh workspace without manual file deletion.
@Injectable()
export class SetupStateService implements OnModuleInit {
    private readonly logger = new Logger(SetupStateService.name);
    private cached: SetupState | null = null;
    // Memoize the platform's currentWorkspace.id lookup so we don't hit
    // the platform on every getState() call. Set once per process boot
    // (or after a successful reset).
    private liveWorkspaceId: string | null = null;
    private workspaceCheckPromise: Promise<void> | null = null;

    constructor(private platform: PlatformGraphqlService) {}

    onModuleInit() {
        this.load();
        // Fire-and-forget the workspace probe so the file gets aligned
        // before the frontend's first GET. Errors are logged but
        // non-fatal — if the platform is down at boot, the legacy
        // unscoped behaviour kicks in until the first reachable probe.
        this.ensureWorkspaceMatch().catch((err) =>
            this.logger.warn(`Initial workspace probe failed: ${err}`),
        );
    }

    getState(): SetupState {
        if (this.cached) return this.cached;
        return this.load();
    }

    // Awaits a workspace check before returning state. The controller
    // calls this so the GET response always reflects the current
    // workspace, not yesterday's.
    async getStateChecked(): Promise<SetupState> {
        await this.ensureWorkspaceMatch();
        return this.getState();
    }

    private async ensureWorkspaceMatch(): Promise<void> {
        // Single-flight: if a check is already running, await it.
        if (this.workspaceCheckPromise) return this.workspaceCheckPromise;
        if (this.liveWorkspaceId) {
            // Already validated this process. Trust the cache.
            return;
        }
        this.workspaceCheckPromise = (async () => {
            try {
                const data = await this.platform.query<{
                    currentWorkspace: { id: string };
                }>(`{ currentWorkspace { id } }`);
                const liveId = data?.currentWorkspace?.id ?? null;
                if (!liveId) {
                    this.logger.warn(
                        'currentWorkspace.id was empty — cannot scope setup-state',
                    );
                    return;
                }
                this.liveWorkspaceId = liveId;
                const current = this.getState();
                if (current.workspaceId && current.workspaceId !== liveId) {
                    this.logger.log(
                        `Workspace changed (${current.workspaceId} → ${liveId}) — resetting setup-state`,
                    );
                    this.resetState();
                }
                if (!current.workspaceId) {
                    // First boot after the workspaceId field was added
                    // (or first boot ever). Stamp the file so future
                    // boots can detect drift.
                    const stamped: SetupState = {
                        ...this.getState(),
                        workspaceId: liveId,
                    };
                    this.writeFile(stamped);
                    this.cached = stamped;
                }
            } finally {
                this.workspaceCheckPromise = null;
            }
        })();
        return this.workspaceCheckPromise;
    }

    // Returns true if any required step is incomplete and the wizard hasn't
    // been explicitly dismissed. Used by the frontend post-login redirect.
    isWizardRequired(): boolean {
        const s = this.getState();
        if (s.wizardDismissed) return false;
        return SETUP_STEP_NAMES.some(name => !s.steps[name].completed);
    }

    markStepCompleted(step: SetupStepName, completedBy: string | null = null): SetupState {
        const current = this.getState();
        if (!current.steps[step]) {
            throw new Error(`Unknown setup step: ${step}`);
        }
        const updated: SetupState = {
            ...current,
            steps: {
                ...current.steps,
                [step]: {
                    completed: true,
                    completedAt: new Date().toISOString(),
                    completedBy,
                },
            },
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        this.writeFile(updated);
        this.cached = updated;
        this.logger.log(`Setup step '${step}' marked completed`);
        return updated;
    }

    markStepIncomplete(step: SetupStepName): SetupState {
        const current = this.getState();
        if (!current.steps[step]) {
            throw new Error(`Unknown setup step: ${step}`);
        }
        const updated: SetupState = {
            ...current,
            steps: {
                ...current.steps,
                [step]: { completed: false, completedAt: null, completedBy: null },
            },
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        this.writeFile(updated);
        this.cached = updated;
        this.logger.log(`Setup step '${step}' marked incomplete`);
        return updated;
    }

    dismissWizard(): SetupState {
        const current = this.getState();
        const updated: SetupState = {
            ...current,
            wizardDismissed: true,
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        this.writeFile(updated);
        this.cached = updated;
        this.logger.log('Setup wizard dismissed');
        return updated;
    }

    resetState(): SetupState {
        // Preserve the live workspaceId on reset so the file remains
        // scoped — otherwise the next workspace check would think the
        // file is unscoped and re-stamp it, which is fine but creates
        // an extra write.
        const fresh: SetupState = {
            ...DEFAULT_SETUP_STATE,
            workspaceId: this.liveWorkspaceId ?? null,
        };
        this.writeFile(fresh);
        this.cached = fresh;
        this.logger.log('Setup state reset to defaults');
        return this.cached;
    }

    private load(): SetupState {
        try {
            if (existsSync(SETUP_STATE_PATH)) {
                const raw = readFileSync(SETUP_STATE_PATH, 'utf8');
                const parsed = JSON.parse(raw);
                // Defensive merge: if a new step name is added later, the old
                // file won't have it. Fill missing steps with the empty default.
                const merged: SetupState = {
                    ...DEFAULT_SETUP_STATE,
                    ...parsed,
                    steps: {
                        ...DEFAULT_SETUP_STATE.steps,
                        ...(parsed.steps ?? {}),
                    },
                };
                this.cached = merged;
                this.logger.log('Setup state loaded from file');
                return merged;
            }
        } catch (err) {
            this.logger.warn(`Failed to load setup state: ${err}`);
        }
        const fresh: SetupState = JSON.parse(JSON.stringify(DEFAULT_SETUP_STATE));
        this.cached = fresh;
        this.logger.log('Using default setup state (no file yet)');
        return fresh;
    }

    private writeFile(state: SetupState) {
        const dir = dirname(SETUP_STATE_PATH);
        if (!existsSync(dir)) mkdirSync(dir, { recursive: true });
        writeFileSync(SETUP_STATE_PATH, JSON.stringify(state, null, 2), 'utf8');
    }
}