import { positionAt } from '../GPS/actions/arena/worldline.js'

export class GpsStorageReader {

    constructor(systemCnx, gpsStorage, debug = false) {
        this.cnx = systemCnx
        this.gpsStorage = gpsStorage
        this.debug = debug
    }

    agentHashKey(agentId) {
        return(this.gpsStorage.agentHashKey.replace(/\[UID\]/g, agentId))
    }

    #parseHashField(raw) {
        if(raw == null) return(null)
        if(typeof(raw) === 'object') return(raw)
        try { return(JSON.parse(raw)) }
        catch { return(null) }
    }

    #segmentToAgent(segment) {
        if(!segment?.id) return(null)
        if(!this.#isVector(segment.position) || !this.#isVector(segment.vector)) return(null)
        return({
            id: segment.id,
            position: { ...segment.position },
            vector: { ...segment.vector },
            since: segment.since ?? 0,
            generation: segment.generation ?? 0,
        })
    }

    #isVector(v) {
        return(
            v &&
            typeof(v) === 'object' &&
            typeof(v.x) === 'number' &&
            typeof(v.y) === 'number' &&
            typeof(v.z) === 'number'
        )
    }

    buildAgentSnapshot(agent, at) {
        return({
            id: agent.id,
            position: positionAt(agent, at),
            vector: { ...agent.vector },
            since: agent.since,
            generation: agent.generation ?? 0,
            t: at,
        })
    }

    async loadSegment(agentId) {
        const raw = await this.cnx.redisHget(this.agentHashKey(agentId), 'segment')
        return(this.#parseHashField(raw))
    }

    async listAgentIds() {
        return(await this.cnx.redisSmembers(this.gpsStorage.agentsIndexKey))
    }

    async loadAllAgents() {
        const ids = await this.listAgentIds()
        const agents = new Map()
        for(const id of ids) {
            const segment = await this.loadSegment(id)
            const agent = this.#segmentToAgent(segment)
            if(agent) agents.set(id, agent)
        }
        return(agents)
    }

    async getAgentPosition(agentId, at) {
        const segment = await this.loadSegment(agentId)
        const agent = this.#segmentToAgent(segment)
        if(!agent) return(null)
        return(this.buildAgentSnapshot(agent, at))
    }

}