import * as childProcess from 'child_process'
import {UniversalPath} from '../util'
import {Inject, Injectable, InjectParam} from '../di'
import {Application} from '../lifecycle/Application'
import {Logging} from '../service/Logging'
import {NodeModule, ExtolloAwareNodeModule} from './types'
import {PackageDiscovered} from './PackageDiscovered'
import {Bus} from './bus'

/**
 * A helper class for discovering and interacting with
 * NPM-style modules.
 */
@Injectable()
export class NodeModules {
    @Inject()
    protected readonly logging!: Logging

    @Inject()
    protected readonly bus!: Bus

    constructor(
        @InjectParam(Application.NODE_MODULES_INJECTION)
        protected readonly manager: string,
    ) { }

    /**
     * Get the NodeModule entry for the base application.
     */
    async app(): Promise<NodeModule> {
        return new Promise<NodeModule>((res, rej) => {
            childProcess.exec(`${this.manager} ls --json`, (error, stdout) => {
                if ( error ) {
                    return rej(error)
                }

                res(JSON.parse(stdout)[0])
            })
        })
    }

    /**
     * Get the path to the node_modules folder for the base application.
     */
    async root(): Promise<UniversalPath> {
        return new Promise<UniversalPath>((res, rej) => {
            childProcess.exec(`${this.manager} root`, (error, stdout) => {
                if ( error ) {
                    return rej(error)
                }

                res(new UniversalPath(stdout.trim()))
            })
        })
    }

    /**
     * Iterate over packages, recursively, starting with the base application's
     * package.json and fire PackageDiscovered events for any that have a valid
     * Extollo discovery entry.
     */
    async discover(): Promise<void> {
        const root = await this.root()
        const module = await this.app()
        return this.discoverRoot(root, module)
    }

    /**
     * Recursively discover child-packages from the node_modules root for the
     * given module.
     *
     * Fires PackageDiscovered events for valid, discovery-enabled packages.
     *
     * @param root - the path to node_modules
     * @param module - the module whose children we are discovering
     * @param seen - used to prevent duplicate packages when recursing
     * @protected
     */
    protected async discoverRoot(root: UniversalPath, module: NodeModule, seen: string[] = []): Promise<void> {
        for ( const key in module.dependencies ) {
            if ( !Object.prototype.hasOwnProperty.call(module.dependencies, key) ) {
                continue
            }

            this.logging.verbose(`Auto-discovery considering package: ${key}`)

            try {
                const packageJson = root.concat(key, 'package.json')
                this.logging.verbose(`Auto-discovery package path: ${packageJson}`)
                if ( await packageJson.exists() ) {
                    const packageJsonString: string = await packageJson.read()
                    const packageJsonData: ExtolloAwareNodeModule = JSON.parse(packageJsonString)
                    if ( !packageJsonData?.extollo?.discover ) {
                        this.logging.debug(`Skipping non-discoverable package: ${key}`)
                        continue
                    }

                    if ( seen.includes(key) ) {
                        this.logging.debug(`Skipping already-discovered package: ${key}`)
                        continue
                    }

                    this.logging.info(`Auto-discovering package: ${key}`)
                    seen.push(key)
                    await this.bus.push(new PackageDiscovered(packageJsonData, packageJson.clone()))

                    const packageNodeModules = packageJson.concat('..', 'node_modules')
                    if ( await packageNodeModules.exists() && packageJsonData?.extollo?.recursiveDependencies?.discover ) {
                        this.logging.debug(`Recursing: ${packageNodeModules}`)
                        await this.discoverRoot(packageNodeModules, packageJsonData, seen)
                    }
                }
            } catch (e: unknown) {
                this.logging.error(`Encountered error while discovering package: ${key}`)
                this.logging.error(e)
            }
        }
    }
}