import { randomId } from '../../utils/random.ts'

export const startChannel = () => {
    const caller = window.name ?? randomId()
    let isDesk = false

    const waitingMessages: Record<string, Pick<PromiseWithResolvers<unknown>, 'reject' | 'resolve'>> = {}
    const messageHandler = ({ data, origin }: MessageEvent) => {
        if (origin.endsWith('.desk.blip.ai')) {
            isDesk = true
        }

        const deferred = waitingMessages[data?.trackingProperties?.id]
        if (deferred) {
            if (data.message?.caller === caller) {
                // This is a echo message, ignore it
                return
            }

            delete waitingMessages[data.trackingProperties.id]
            if (data.error) {
                deferred.reject(JSON.parse(data.error))
            } else {
                deferred.resolve(data.response)
            }
        }
    }
    window.addEventListener('message', messageHandler)

    let isDestroyed = false
    return {
        get isDesk() {
            return isDesk
        },
        post: <T>(action: string, content: unknown, options?: { fireAndForget: T extends void ? never : true }) => {
            if (isDestroyed) {
                throw new Error('Channel is destroyed')
            }

            const id = randomId()

            let promise: Promise<unknown>
            if (options?.fireAndForget) {
                promise = Promise.resolve()
            } else {
                const deferred = Promise.withResolvers()
                waitingMessages[id] = { reject: deferred.reject, resolve: deferred.resolve }
                promise = deferred.promise
            }

            window.parent.postMessage(
                {
                    message: {
                        action: `blipEvent:${action}`,
                        content,
                        caller,
                    },
                    trackingProperties: {
                        id,
                    },
                },
                '*',
            )

            return promise as Promise<T>
        },
        destroy: () => {
            window.removeEventListener('message', messageHandler)
            isDestroyed = true
        },
    }
}