import {isIPv4, isIPv6} from 'node:net'
import {
    ChangeResourceRecordSetsCommand,
    CreateHostedZoneCommand,
    DeleteHostedZoneCommand,
    GetHostedZoneCommand,
    ListHostedZonesCommand,
    ListResourceRecordSetsCommand,
    type HostedZone,
    type ResourceRecordSet,
    type Route53Client,
    type RRType,
} from '@aws-sdk/client-route-53'
import type {ChildItem, CollectionPage, ItemStoreAdapter, PageQuery} from '../cloud-spi/childCollections'
import {DNS_RECORD_TYPES, DNS_ZONE_NAME_PATTERN, awsDnsSchema} from '../cloud-spi/dnsSchema'
import {ConflictError, NotFoundError, ValidationError} from '../cloud-spi/errors'
import type {CloudResource, CloudServiceAdapter, CreateResourceInput, ResourceQuery, ServiceSchema} from '../cloud-spi/types'

/** Route 53 caps ListResourceRecordSets pages at 300 and ListHostedZones at 100. */
const RECORD_PAGE_LIMIT = 300
const ZONE_PAGE_LIMIT = 100
/** Route 53's TTL range. */
const MAX_TTL = 2_147_483_647

/**
 * Talks to Route 53 hosted zones, verified against Floci core (community, `latest`).
 *
 * Notes from probing the runtime:
 *  - Zone IDs come back as `/hostedzone/Z…`; the bare ID is accepted everywhere, so
 *    resources are keyed by it.
 *  - A new zone holds the apex NS and SOA records, and `DeleteHostedZone` refuses
 *    with `HostedZoneNotEmpty` (400) while any other record remains, as on AWS.
 *  - A missing zone is `NoSuchHostedZone` with HTTP 404.
 *  - The runtime stores record values without checking them (an A record of
 *    `not-an-ip`, unquoted TXT text), so the AWS rules are applied here.
 *
 * Records are the zone's child items, keyed by name, type and set identifier,
 * which is what makes a record set unique in Route 53.
 */
export class AwsDnsAdapter implements CloudServiceAdapter {
    readonly cloud = 'aws' as const
    readonly service = 'dns' as const
    readonly items: ItemStoreAdapter

    constructor(private readonly route53: Route53Client, private readonly region = 'us-east-1') {
        this.items = new RecordStore(route53, (id) => this.zoneName(id))
    }

    schema(): ServiceSchema {
        return awsDnsSchema()
    }

    async list(query: ResourceQuery = {}): Promise<CloudResource[]> {
        const zones: HostedZone[] = []
        let marker: string | undefined
        do {
            const res = await this.route53.send(new ListHostedZonesCommand({MaxItems: ZONE_PAGE_LIMIT, ...(marker ? {Marker: marker} : {})}))
            zones.push(...(res.HostedZones ?? []))
            marker = res.IsTruncated ? res.NextMarker : undefined
        } while (marker)

        const search = query.search?.trim().toLowerCase()
        return zones.map((zone) => toResource(zone))
            .filter((zone) => !search || zone.name.toLowerCase().includes(search) || zone.id.toLowerCase().includes(search))
    }

    async get(id: string): Promise<CloudResource | null> {
        try {
            const res = await this.route53.send(new GetHostedZoneCommand({Id: zoneId(id)}))
            return res.HostedZone ? toResource(res.HostedZone, res.DelegationSet?.NameServers, res.VPCs?.map((vpc) => `${vpc.VPCId} (${vpc.VPCRegion})`)) : null
        } catch (error) {
            if (errorName(error) === 'NoSuchHostedZone') return null
            throw error
        }
    }

    async create(input: CreateResourceInput): Promise<CloudResource> {
        const name = typeof input.values.name === 'string' ? input.values.name.trim().toLowerCase() : ''
        if (!new RegExp(DNS_ZONE_NAME_PATTERN).test(name)) throw new ValidationError('name must be a domain name such as example.com')
        const comment = typeof input.values.comment === 'string' ? input.values.comment.trim() : ''
        const vpcId = typeof input.values.vpcId === 'string' ? input.values.vpcId.trim() : ''
        if (vpcId && !/^vpc-[0-9a-f]{8,17}$/.test(vpcId)) throw new ValidationError('vpcId must be a VPC ID such as vpc-0abc1234')

        const res = await this.route53.send(new CreateHostedZoneCommand({
            Name: name,
            CallerReference: crypto.randomUUID(),
            HostedZoneConfig: {Comment: comment || undefined, PrivateZone: Boolean(vpcId)},
            ...(vpcId ? {VPC: {VPCId: vpcId, VPCRegion: this.region as never}} : {}),
        }))
        if (!res.HostedZone) throw new ValidationError(`Route 53 did not return the hosted zone ${name}`)
        return toResource(res.HostedZone, res.DelegationSet?.NameServers, vpcId ? [`${vpcId} (${this.region})`] : undefined)
    }

    async delete(id: string): Promise<void> {
        try {
            await this.route53.send(new DeleteHostedZoneCommand({Id: zoneId(id)}))
        } catch (error) {
            if (errorName(error) === 'HostedZoneNotEmpty') {
                throw new ConflictError('Delete the zone\'s records first: Route 53 only deletes a hosted zone that holds just its NS and SOA records')
            }
            throw error
        }
    }

    private async zoneName(id: string): Promise<string> {
        const zone = await this.get(id)
        if (!zone) throw new NotFoundError(`Hosted zone ${id} was not found`)
        return zone.name
    }
}

class RecordStore implements ItemStoreAdapter {
    constructor(private readonly route53: Route53Client, private readonly zoneName: (id: string) => Promise<string>) {}

    async listItems(resourceId: string, page: PageQuery = {}): Promise<CollectionPage<ChildItem>> {
        const start = decodeCursor(page.cursor)
        const res = await this.route53.send(new ListResourceRecordSetsCommand({
            HostedZoneId: zoneId(resourceId),
            MaxItems: Math.min(page.limit ?? RECORD_PAGE_LIMIT, RECORD_PAGE_LIMIT),
            ...(start ? {StartRecordName: start.name, StartRecordType: start.type as RRType, StartRecordIdentifier: start.identifier} : {}),
        }))
        const zone = await this.zoneName(resourceId)
        return {
            items: (res.ResourceRecordSets ?? []).map((record) => toRecordItem(record, zone)),
            nextCursor: res.IsTruncated && res.NextRecordName
                ? encodeCursor({name: res.NextRecordName, type: res.NextRecordType ?? '', identifier: res.NextRecordIdentifier})
                : null,
        }
    }

    /** Creates the record set, or replaces the one with the same name and type (UPSERT). */
    async putItem(resourceId: string, body: Record<string, unknown>): Promise<ChildItem> {
        const zone = await this.zoneName(resourceId)
        const record = recordFromInput(body, zone)
        await this.route53.send(new ChangeResourceRecordSetsCommand({
            HostedZoneId: zoneId(resourceId),
            ChangeBatch: {Changes: [{Action: 'UPSERT', ResourceRecordSet: record}]},
        }))
        return toRecordItem(record, zone)
    }

    /** Route 53 deletes a record set only when given it exactly, so the stored set is read first. */
    async deleteItem(resourceId: string, itemId: string): Promise<void> {
        const key = parseRecordId(itemId)
        const zone = await this.zoneName(resourceId)
        if (key.name === zone && (key.type === 'NS' || key.type === 'SOA')) {
            throw new ConflictError(`The zone's own ${key.type} record cannot be deleted`)
        }
        const res = await this.route53.send(new ListResourceRecordSetsCommand({
            HostedZoneId: zoneId(resourceId),
            StartRecordName: key.name,
            StartRecordType: key.type as RRType,
            ...(key.identifier ? {StartRecordIdentifier: key.identifier} : {}),
            MaxItems: 1,
        }))
        const stored = res.ResourceRecordSets?.find((record) => recordId(record) === itemId)
        if (!stored) throw new NotFoundError(`Record ${key.type} ${key.name} was not found`)
        await this.route53.send(new ChangeResourceRecordSetsCommand({
            HostedZoneId: zoneId(resourceId),
            ChangeBatch: {Changes: [{Action: 'DELETE', ResourceRecordSet: stored}]},
        }))
    }
}

function toResource(zone: HostedZone, nameServers?: string[], vpcs?: string[]): CloudResource {
    const id = zoneId(zone.Id ?? '')
    const privateZone = zone.Config?.PrivateZone ?? false
    return {
        id,
        name: withoutDot(zone.Name ?? id),
        cloud: 'aws',
        service: 'dns',
        type: 'hosted-zone',
        region: null,
        createdAt: null,
        status: null,
        metadata: {
            visibility: privateZone ? 'private' : 'public',
            recordCount: zone.ResourceRecordSetCount ?? null,
            comment: zone.Config?.Comment ?? null,
            ...(nameServers ? {nameServers} : {}),
            ...(vpcs ? {vpcs} : {}),
        },
    }
}

function toRecordItem(record: ResourceRecordSet, zone: string): ChildItem {
    const name = withoutDot(unescapeName(record.Name ?? ''))
    return {
        id: recordId(record),
        collectionId: null,
        timestamp: null,
        body: {
            name,
            type: record.Type ?? '',
            ttl: record.TTL ?? null,
            values: (record.ResourceRecords ?? []).map((value) => value.Value ?? ''),
            alias: record.AliasTarget ? {dnsName: withoutDot(record.AliasTarget.DNSName ?? ''), hostedZoneId: record.AliasTarget.HostedZoneId ?? '', evaluateTargetHealth: record.AliasTarget.EvaluateTargetHealth ?? false} : null,
            setIdentifier: record.SetIdentifier ?? null,
            // The zone's own NS and SOA records, and routing-policy sets this console cannot edit faithfully.
            managed: (name === zone && (record.Type === 'NS' || record.Type === 'SOA')),
            editable: !record.AliasTarget && !record.SetIdentifier,
        },
        metadata: {},
    }
}

/** Validates a simple record the way Route 53 does and returns it as a record set. */
function recordFromInput(body: Record<string, unknown>, zone: string): ResourceRecordSet {
    const type = typeof body.type === 'string' ? body.type.trim().toUpperCase() : ''
    if (!(DNS_RECORD_TYPES as readonly string[]).includes(type)) throw new ValidationError(`type must be one of ${DNS_RECORD_TYPES.join(', ')}`)

    const name = qualifiedName(typeof body.name === 'string' ? body.name : '', zone)
    const ttl = Number(body.ttl ?? 300)
    if (!Number.isInteger(ttl) || ttl < 0 || ttl > MAX_TTL) throw new ValidationError('ttl must be a whole number of seconds')

    const rawValues = Array.isArray(body.values) ? body.values : typeof body.values === 'string' ? body.values.split('\n') : []
    const values = rawValues.map((value) => String(value).trim()).filter(Boolean)
    if (values.length === 0) throw new ValidationError('Add at least one value')
    if (type === 'CNAME' && values.length > 1) throw new ValidationError('A CNAME record has exactly one value')
    if (type === 'CNAME' && name === zone) throw new ValidationError('The zone apex cannot have a CNAME record; use an A or alias record')
    for (const value of values) {
        if (type === 'A' && !isIPv4(value)) throw new ValidationError(`${value} is not an IPv4 address`)
        if (type === 'AAAA' && !isIPv6(value)) throw new ValidationError(`${value} is not an IPv6 address`)
        if (type === 'MX' && !/^\d{1,5}\s+\S+$/.test(value)) throw new ValidationError(`MX values are a priority and a mail server, such as "10 mail.${zone}"`)
    }

    return {
        Name: name,
        Type: type as RRType,
        TTL: ttl,
        ResourceRecords: values.map((value) => ({Value: type === 'TXT' || type === 'SPF' ? quoted(value) : value})),
    }
}

/** "www", "www.example.com" and "@" all name a record in example.com. */
function qualifiedName(input: string, zone: string): string {
    const name = withoutDot(input.trim().toLowerCase())
    if (!name || name === '@') return zone
    const full = name === zone || name.endsWith(`.${zone}`) ? name : `${name}.${zone}`
    if (!/^(\*\.)?([a-z0-9_](?:[a-z0-9_-]{0,61}[a-z0-9_])?\.)*[a-z0-9_](?:[a-z0-9_-]{0,61}[a-z0-9_])?$/.test(full) || full.length > 253) {
        throw new ValidationError(`${input} is not a valid record name`)
    }
    return full
}

/** Route 53 wants each TXT string quoted; text the user already quoted is kept as written. */
function quoted(value: string): string {
    if (value.startsWith('"') && value.endsWith('"') && value.length > 1) return value
    return `"${value.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"`
}

function recordId(record: Pick<ResourceRecordSet, 'Name' | 'Type' | 'SetIdentifier'>): string {
    return [withoutDot(unescapeName(record.Name ?? '')), record.Type ?? '', ...(record.SetIdentifier ? [record.SetIdentifier] : [])].join('|')
}

function parseRecordId(id: string): {name: string; type: string; identifier?: string} {
    const [name, type, ...rest] = id.split('|')
    if (!name || !type) throw new ValidationError('Record id must be name|type')
    return {name, type, ...(rest.length ? {identifier: rest.join('|')} : {})}
}

function encodeCursor(cursor: {name: string; type: string; identifier?: string}): string {
    return Buffer.from(JSON.stringify(cursor)).toString('base64url')
}

function decodeCursor(cursor: string | undefined): {name: string; type: string; identifier?: string} | null {
    if (!cursor) return null
    try {
        const value = JSON.parse(Buffer.from(cursor, 'base64url').toString()) as {name?: unknown; type?: unknown; identifier?: unknown}
        if (typeof value.name !== 'string' || typeof value.type !== 'string') throw new Error('bad cursor')
        return {name: value.name, type: value.type, ...(typeof value.identifier === 'string' ? {identifier: value.identifier} : {})}
    } catch {
        throw new ValidationError('cursor is not valid for this hosted zone')
    }
}

/** Route 53 returns `*` as `\052` and other special characters as octal escapes. */
function unescapeName(name: string): string {
    return name.replace(/\\(\d{3})/g, (_match, octal: string) => String.fromCharCode(parseInt(octal, 8)))
}

function zoneId(id: string): string {
    return id.replace(/^\/hostedzone\//, '')
}

function withoutDot(name: string): string {
    return name.endsWith('.') ? name.slice(0, -1) : name
}

function errorName(error: unknown): string {
    return (error as {name?: string} | null)?.name ?? ''
}