import { OsmNode, OsmObject, OsmRelation, OsmWay } from "./OsmObject"
import { Store, UIEventSource } from "../UIEventSource"
import Constants from "../../Models/Constants"
import OsmChangeAction from "./Actions/OsmChangeAction"
import { ChangeDescription, ChangeDescriptionTools } from "./Actions/ChangeDescription"
import { Utils } from "../../Utils"
import { LocalStorageSource } from "../Web/LocalStorageSource"
import SimpleMetaTagger from "../SimpleMetaTagger"
import { FeatureSource, IndexedFeatureSource } from "../FeatureSource/FeatureSource"
import { GeoLocationPointProperties } from "../State/GeoLocationState"
import { GeoOperations } from "../GeoOperations"
import { ChangesetHandler, ChangesetTag } from "./ChangesetHandler"
import { OsmConnection } from "./OsmConnection"
import FeaturePropertiesStore from "../FeatureSource/Actors/FeaturePropertiesStore"
import OsmObjectDownloader from "./OsmObjectDownloader"

/**
 * Handles all changes made to OSM.
 * Needs an authenticator via OsmConnection
 */
export class Changes {
    public readonly pendingChanges: UIEventSource<ChangeDescription[]> =
        LocalStorageSource.GetParsed<ChangeDescription[]>("pending-changes", [])
    public readonly allChanges = new UIEventSource<ChangeDescription[]>(undefined)
    public readonly state: { allElements?: IndexedFeatureSource; osmConnection: OsmConnection }
    public readonly extraComment: UIEventSource<string> = new UIEventSource(undefined)
    public readonly backend: string
    public readonly isUploading = new UIEventSource(false)
    private readonly historicalUserLocations?: FeatureSource
    private _nextId: number = -1 // Newly assigned ID's are negative
    private readonly previouslyCreated: OsmObject[] = []
    private readonly _leftRightSensitive: boolean
    private readonly _changesetHandler: ChangesetHandler

    constructor(
        state: {
            dryRun: Store<boolean>
            allElements?: IndexedFeatureSource
            featurePropertiesStore?: FeaturePropertiesStore
            osmConnection: OsmConnection
            historicalUserLocations?: FeatureSource
        },
        leftRightSensitive: boolean = false
    ) {
        this._leftRightSensitive = leftRightSensitive
        // We keep track of all changes just as well
        this.allChanges.setData([...this.pendingChanges.data])
        // If a pending change contains a negative ID, we save that
        this._nextId = Math.min(-1, ...(this.pendingChanges.data?.map((pch) => pch.id) ?? []))
        this.state = state
        this.backend = state.osmConnection.Backend()
        this._changesetHandler = new ChangesetHandler(
            state.dryRun,
            state.osmConnection,
            state.featurePropertiesStore,
            this
        )
        this.historicalUserLocations = state.historicalUserLocations

        // Note: a changeset might be reused which was opened just before and might have already used some ids
        // This doesn't matter however, as the '-1' is per piecewise upload, not global per changeset
    }

    static createChangesetFor(
        csId: string,
        allChanges: {
            modifiedObjects: OsmObject[]
            newObjects: OsmObject[]
            deletedObjects: OsmObject[]
        }
    ): string {
        const changedElements = allChanges.modifiedObjects ?? []
        const newElements = allChanges.newObjects ?? []
        const deletedElements = allChanges.deletedObjects ?? []

        let changes = `<osmChange version='0.6' generator='Mapcomplete ${Constants.vNumber}'>`
        if (newElements.length > 0) {
            changes +=
                "\n<create>\n" +
                newElements.map((e) => e.ChangesetXML(csId)).join("\n") +
                "</create>"
        }
        if (changedElements.length > 0) {
            changes +=
                "\n<modify>\n" +
                changedElements.map((e) => e.ChangesetXML(csId)).join("\n") +
                "\n</modify>"
        }

        if (deletedElements.length > 0) {
            changes +=
                "\n<delete>\n" +
                deletedElements.map((e) => e.ChangesetXML(csId)).join("\n") +
                "\n</delete>"
        }

        changes += "</osmChange>"
        return changes
    }

    private static GetNeededIds(changes: ChangeDescription[]) {
        return Utils.Dedup(changes.filter((c) => c.id >= 0).map((c) => c.type + "/" + c.id))
    }

    /**
     * Returns a new ID and updates the value for the next ID
     */
    public getNewID() {
        return this._nextId--
    }

    /**
     * Uploads all the pending changes in one go.
     * Triggered by the 'PendingChangeUploader'-actor in Actors
     */
    public async flushChanges(flushreason: string = undefined): Promise<void> {
        if (this.pendingChanges.data.length === 0) {
            return
        }
        if (this.isUploading.data) {
            console.log("Is already uploading... Abort")
            return
        }

        console.log("Uploading changes due to: ", flushreason)
        this.isUploading.setData(true)
        try {
            const csNumber = await this.flushChangesAsync()
            this.isUploading.setData(false)
            console.log("Changes flushed. Your changeset is " + csNumber)
        } catch (e) {
            this.isUploading.setData(false)
            console.error("Flushing changes failed due to", e)
        }
    }

    public async applyAction(action: OsmChangeAction): Promise<void> {
        const changeDescriptions = await action.Perform(this)
        changeDescriptions[0].meta.distanceToObject = this.calculateDistanceToChanges(
            action,
            changeDescriptions
        )
        this.applyChanges(changeDescriptions)
    }

    public applyChanges(changes: ChangeDescription[]) {
        console.log("Received changes:", changes)
        this.pendingChanges.data.push(...changes)
        this.pendingChanges.ping()
        this.allChanges.data.push(...changes)
        this.allChanges.ping()
    }

    public CreateChangesetObjects(
        changes: ChangeDescription[],
        downloadedOsmObjects: OsmObject[]
    ): {
        newObjects: OsmObject[]
        modifiedObjects: OsmObject[]
        deletedObjects: OsmObject[]
    } {
        const objects: Map<string, OsmObject> = new Map<string, OsmObject>()
        const states: Map<string, "unchanged" | "created" | "modified" | "deleted"> = new Map()

        for (const o of downloadedOsmObjects) {
            objects.set(o.type + "/" + o.id, o)
            states.set(o.type + "/" + o.id, "unchanged")
        }

        for (const o of this.previouslyCreated) {
            objects.set(o.type + "/" + o.id, o)
            states.set(o.type + "/" + o.id, "unchanged")
        }

        for (const change of changes) {
            let changed = false
            const id = change.type + "/" + change.id
            if (!objects.has(id)) {
                // The object hasn't been seen before, so it doesn't exist yet and is newly created by its very definition
                if (change.id >= 0) {
                    // Might be a failed fetch for simply this object
                    throw "Did not get an object that should be known: " + id
                }
                if (change.changes === undefined) {
                    // This object is a change to a newly created object. However, we have not seen the creation changedescription yet!
                    throw "Not a creation of the object"
                }
                // This is a new object that should be created
                states.set(id, "created")
                console.log("Creating object for changeDescription", change)
                let osmObj: OsmObject = undefined
                switch (change.type) {
                    case "node":
                        const n = new OsmNode(change.id)
                        n.lat = change.changes["lat"]
                        n.lon = change.changes["lon"]
                        osmObj = n
                        break
                    case "way":
                        const w = new OsmWay(change.id)
                        w.nodes = change.changes["nodes"]
                        osmObj = w
                        break
                    case "relation":
                        const r = new OsmRelation(change.id)
                        r.members = change.changes["members"]
                        osmObj = r
                        break
                }
                if (osmObj === undefined) {
                    throw "Hmm? This is a bug"
                }
                objects.set(id, osmObj)
                this.previouslyCreated.push(osmObj)
            }

            const state = states.get(id)
            if (change.doDelete) {
                if (state === "created") {
                    states.set(id, "unchanged")
                } else {
                    states.set(id, "deleted")
                }
            }

            const obj = objects.get(id)
            // Apply tag changes
            for (const kv of change.tags ?? []) {
                const k = kv.k
                let v = kv.v

                if (v === "") {
                    v = undefined
                }

                const oldV = obj.tags[k]
                if (oldV === v) {
                    continue
                }

                obj.tags[k] = v
                changed = true
            }

            if (change.changes !== undefined) {
                switch (change.type) {
                    case "node":
                        // @ts-ignore
                        const nlat = Utils.Round7(change.changes.lat)
                        // @ts-ignore
                        const nlon = Utils.Round7(change.changes.lon)
                        const n = <OsmNode>obj
                        if (n.lat !== nlat || n.lon !== nlon) {
                            console.log("Node moved:", n.lat, nlat, n.lon, nlon)
                            n.lat = nlat
                            n.lon = nlon
                            changed = true
                        }
                        break
                    case "way":
                        const nnodes = change.changes["nodes"]
                        const w = <OsmWay>obj
                        if (!Utils.Identical(nnodes, w.nodes)) {
                            w.nodes = nnodes
                            changed = true
                        }
                        break
                    case "relation":
                        const nmembers: {
                            type: "node" | "way" | "relation"
                            ref: number
                            role: string
                        }[] = change.changes["members"]
                        const r = <OsmRelation>obj
                        if (
                            !Utils.Identical(nmembers, r.members, (a, b) => {
                                return a.role === b.role && a.type === b.type && a.ref === b.ref
                            })
                        ) {
                            r.members = nmembers
                            changed = true
                        }
                        break
                }
            }

            if (changed && states.get(id) === "unchanged") {
                states.set(id, "modified")
            }
        }

        const result = {
            newObjects: [],
            modifiedObjects: [],
            deletedObjects: [],
        }

        objects.forEach((v, id) => {
            const state = states.get(id)
            if (state === "created") {
                result.newObjects.push(v)
            }
            if (state === "modified") {
                result.modifiedObjects.push(v)
            }
            if (state === "deleted") {
                result.deletedObjects.push(v)
            }
        })

        console.debug(
            "Calculated the pending changes: ",
            result.newObjects.length,
            "new; ",
            result.modifiedObjects.length,
            "modified;",
            result.deletedObjects,
            "deleted"
        )
        return result
    }

    private calculateDistanceToChanges(
        change: OsmChangeAction,
        changeDescriptions: ChangeDescription[]
    ) {
        const locations = this.historicalUserLocations?.features?.data
        if (locations === undefined) {
            // No state loaded or no locations -> we can't calculate...
            return
        }
        if (!change.trackStatistics) {
            // Probably irrelevant, such as a new helper node
            return
        }

        const now = new Date()
        const recentLocationPoints = locations
            .filter((feat) => feat.geometry.type === "Point")
            .filter((feat) => {
                const visitTime = new Date(
                    (<GeoLocationPointProperties>(<any>feat.properties)).date
                )
                // In seconds
                const diff = (now.getTime() - visitTime.getTime()) / 1000
                return diff < Constants.nearbyVisitTime
            })
        if (recentLocationPoints.length === 0) {
            // Probably no GPS enabled/no fix
            return
        }

        // The applicable points, contain information in their properties about location, time and GPS accuracy
        // They are all GeoLocationPointProperties
        // We walk every change and determine the closest distance possible
        // Only if the change itself does _not_ contain any coordinates, we fall back and search the original feature in the state

        const changedObjectCoordinates: [number, number][] = []

        {
            const feature = this.state.allElements?.featuresById?.data.get(change.mainObjectId)
            if (feature !== undefined) {
                changedObjectCoordinates.push(GeoOperations.centerpointCoordinates(feature))
            }
        }

        for (const changeDescription of changeDescriptions) {
            const chng:
                | { lat: number; lon: number }
                | { coordinates: [number, number][] }
                | { members } = changeDescription.changes
            if (chng === undefined) {
                continue
            }
            if (chng["lat"] !== undefined) {
                changedObjectCoordinates.push([chng["lat"], chng["lon"]])
            }
            if (chng["coordinates"] !== undefined) {
                changedObjectCoordinates.push(...chng["coordinates"])
            }
        }

        return Math.min(
            ...changedObjectCoordinates.map((coor) =>
                Math.min(
                    ...recentLocationPoints.map((gpsPoint) => {
                        const otherCoor = GeoOperations.centerpointCoordinates(gpsPoint)
                        return GeoOperations.distanceBetween(coor, otherCoor)
                    })
                )
            )
        )
    }

    /**
     * Upload the selected changes to OSM.
     * Returns 'true' if successful and if they can be removed
     */
    private async flushSelectChanges(
        pending: ChangeDescription[],
        openChangeset: UIEventSource<number>
    ): Promise<boolean> {
        const self = this
        const neededIds = Changes.GetNeededIds(pending)
        // We _do not_ pass in the Changes object itself - we want the data from OSM directly in order to apply the changes
        const downloader = new OsmObjectDownloader(this.backend, undefined)
        let osmObjects = await Promise.all<{ id: string; osmObj: OsmObject | "deleted" }>(
            neededIds.map(async (id) => {
                try {
                    const osmObj = await downloader.DownloadObjectAsync(id)
                    return { id, osmObj }
                } catch (e) {
                    console.error(
                        "Could not download OSM-object",
                        id,
                        " dropping it from the changes (" + e + ")"
                    )
                    return undefined
                }
            })
        )

        osmObjects = Utils.NoNull(osmObjects)

        for (const { osmObj, id } of osmObjects) {
            if (osmObj === "deleted") {
                pending = pending.filter((ch) => ch.type + "/" + ch.id !== id)
            }
        }

        const objects = osmObjects
            .filter((obj) => obj.osmObj !== "deleted")
            .map((obj) => <OsmObject>obj.osmObj)

        if (this._leftRightSensitive) {
            objects.forEach((obj) => SimpleMetaTagger.removeBothTagging(obj.tags))
        }

        console.log("Got the fresh objects!", objects, "pending: ", pending)
        if (pending.length == 0) {
            console.log("No pending changes...")
            return true
        }

        const perType = Array.from(
            Utils.Hist(
                pending
                    .filter(
                        (descr) =>
                            descr.meta.changeType !== undefined && descr.meta.changeType !== null
                    )
                    .map((descr) => descr.meta.changeType)
            ),
            ([key, count]) => ({
                key: key,
                value: count,
                aggregate: true,
            })
        )
        const motivations = pending
            .filter((descr) => descr.meta.specialMotivation !== undefined)
            .map((descr) => ({
                key: descr.meta.changeType + ":" + descr.type + "/" + descr.id,
                value: descr.meta.specialMotivation,
            }))

        const distances = Utils.NoNull(pending.map((descr) => descr.meta.distanceToObject))
        distances.sort((a, b) => a - b)
        const perBinCount = Constants.distanceToChangeObjectBins.map((_) => 0)

        let j = 0
        const maxDistances = Constants.distanceToChangeObjectBins
        for (let i = 0; i < maxDistances.length; i++) {
            const maxDistance = maxDistances[i]
            // distances is sorted in ascending order, so as soon as one is to big, all the resting elements will be bigger too
            while (j < distances.length && distances[j] < maxDistance) {
                perBinCount[i]++
                j++
            }
        }

        const perBinMessage = Utils.NoNull(
            perBinCount.map((count, i) => {
                if (count === 0) {
                    return undefined
                }
                const maxD = maxDistances[i]
                let key = `change_within_${maxD}m`
                if (maxD === Number.MAX_VALUE) {
                    key = `change_over_${maxDistances[i - 1]}m`
                }
                return {
                    key,
                    value: count,
                    aggregate: true,
                }
            })
        )

        // This method is only called with changedescriptions for this theme
        const theme = pending[0].meta.theme
        let comment = "Adding data with #MapComplete for theme #" + theme
        if (this.extraComment.data !== undefined) {
            comment += "\n\n" + this.extraComment.data
        }

        const metatags: ChangesetTag[] = [
            {
                key: "comment",
                value: comment,
            },
            {
                key: "theme",
                value: theme,
            },
            ...perType,
            ...motivations,
            ...perBinMessage,
        ]

        await this._changesetHandler.UploadChangeset(
            (csId, remappings) => {
                if (remappings.size > 0) {
                    console.log("Rewriting pending changes from", pending, "with", remappings)
                    pending = pending.map((ch) => ChangeDescriptionTools.rewriteIds(ch, remappings))
                    console.log("Result is", pending)
                }
                const changes: {
                    newObjects: OsmObject[]
                    modifiedObjects: OsmObject[]
                    deletedObjects: OsmObject[]
                } = self.CreateChangesetObjects(pending, objects)
                return Changes.createChangesetFor("" + csId, changes)
            },
            metatags,
            openChangeset
        )

        console.log("Upload successfull!")
        return true
    }

    private async flushChangesAsync(): Promise<void> {
        const self = this
        try {
            // At last, we build the changeset and upload
            const pending = self.pendingChanges.data

            const pendingPerTheme = new Map<string, ChangeDescription[]>()
            for (const changeDescription of pending) {
                const theme = changeDescription.meta.theme
                if (!pendingPerTheme.has(theme)) {
                    pendingPerTheme.set(theme, [])
                }
                pendingPerTheme.get(theme).push(changeDescription)
            }

            const successes = await Promise.all(
                Array.from(pendingPerTheme, async ([theme, pendingChanges]) => {
                    try {
                        const openChangeset = this.state.osmConnection
                            .GetPreference("current-open-changeset-" + theme)
                            .sync(
                                (str) => {
                                    const n = Number(str)
                                    if (isNaN(n)) {
                                        return undefined
                                    }
                                    return n
                                },
                                [],
                                (n) => "" + n
                            )
                        console.log(
                            "Using current-open-changeset-" +
                                theme +
                                " from the preferences, got " +
                                openChangeset.data
                        )

                        return await self.flushSelectChanges(pendingChanges, openChangeset)
                    } catch (e) {
                        console.error("Could not upload some changes:", e)
                        return false
                    }
                })
            )

            if (!successes.some((s) => s == false)) {
                // All changes successfull, we clear the data!
                this.pendingChanges.setData([])
            }
        } catch (e) {
            console.error(
                "Could not handle changes - probably an old, pending changeset in localstorage with an invalid format; erasing those",
                e
            )
            self.pendingChanges.setData([])
        } finally {
            self.isUploading.setData(false)
        }
    }
}