const hasValue = (value: unknown) => value !== null && value !== undefined && value !== ""

const stringArg = (args: Record<string, unknown>, key: string) => {
    const value = args[key]
    return typeof value === "string" && value.trim() ? value.trim() : null
}

const statementAllocationTargetFields = [
    "createddocument",
    "incominginvoice",
    "account",
    "ownaccount",
    "customer",
    "vendor",
] as const

const manualDebitFields = ["account", "customer", "vendor", "ownaccount"] as const
const manualCreditFields = ["contraAccount", "contraCustomer", "contraVendor", "contraOwnaccount"] as const
const bookingModes = new Set(["expense", "depreciation_single", "depreciation_bundle"])
const depreciationMethods = new Set(["linear", "degressive"])

const requiredNumber = (args: Record<string, unknown>, key: string) => {
    const value = Number(args[key])
    if (!hasValue(args[key]) || !Number.isFinite(value)) throw new Error(`${key} muss eine gültige Zahl sein`)
    return value
}

const optionalNumericId = (args: Record<string, unknown>, key: string) => {
    if (!hasValue(args[key])) return undefined
    const value = Number(args[key])
    if (!Number.isInteger(value) || value <= 0) throw new Error(`${key} muss eine gültige ID sein`)
    return value
}

export const statementAllocationUuidArg = (args: Record<string, unknown>, key: string) => {
    if (!hasValue(args[key])) return undefined
    const value = String(args[key]).trim()
    if (!/^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(value)) {
        throw new Error(`${key} muss eine gültige UUID sein`)
    }
    return value
}

const validDate = (value: string | null) =>
    Boolean(value && /^\d{4}-\d{2}-\d{2}$/.test(value) && !Number.isNaN(Date.parse(`${value}T00:00:00Z`)))

export const prepareStatementAllocationInput = (args: Record<string, unknown>) => {
    const payload: Record<string, any> = {}
    const amount = requiredNumber(args, "amount")
    const bankstatement = optionalNumericId(args, "bankstatement")
    const bookingMode = stringArg(args, "bookingMode") || "expense"

    if (!bookingModes.has(bookingMode)) throw new Error(`Ungültige Aufwandsart: ${bookingMode}`)

    payload.amount = amount
    if (args.description !== undefined) payload.description = stringArg(args, "description")
    payload.bookingMode = bookingMode
    if (args.datevTaxKey !== undefined) payload.datevTaxKey = stringArg(args, "datevTaxKey")

    for (const field of ["createddocument", "incominginvoice", "account", "customer", "vendor"] as const) {
        const value = optionalNumericId(args, field)
        if (value !== undefined) payload[field] = value
    }
    for (const field of ["ownaccount", "contraOwnaccount"] as const) {
        const value = statementAllocationUuidArg(args, field)
        if (value !== undefined) payload[field] = value
    }
    for (const field of ["contraAccount", "contraCustomer", "contraVendor"] as const) {
        const value = optionalNumericId(args, field)
        if (value !== undefined) payload[field] = value
    }

    if (bankstatement !== undefined) {
        const selectedTargets = statementAllocationTargetFields.filter((field) => hasValue(payload[field]))
        if (selectedTargets.length !== 1) {
            throw new Error("Für eine Bankzuweisung muss genau ein Ziel ausgewählt werden")
        }
        if (amount === 0) throw new Error("Der Zuweisungsbetrag darf nicht 0 sein")
        if (manualCreditFields.some((field) => hasValue(payload[field]))) {
            throw new Error("Haben-Konten sind nur bei manuellen Buchungen zulässig")
        }

        payload.bankstatement = bankstatement
    } else {
        const manualBookingDate = stringArg(args, "manualBookingDate")
        if (!validDate(manualBookingDate)) {
            throw new Error("Für manuelle Buchungen ist ein gültiges Buchungsdatum erforderlich")
        }
        if (amount <= 0) throw new Error("Für manuelle Buchungen muss der Betrag größer als 0 sein")

        const manualInvoiceSide = stringArg(args, "manualInvoiceSide")
        const hasInvoice = hasValue(payload.incominginvoice)
        if (hasInvoice && manualInvoiceSide !== "debit" && manualInvoiceSide !== "credit") {
            throw new Error("Für zugewiesene Eingangsbelege muss Soll oder Haben ausgewählt sein")
        }
        if (!hasInvoice && manualInvoiceSide) {
            throw new Error("manualInvoiceSide ist nur zusammen mit incominginvoice zulässig")
        }

        const debitCount = manualDebitFields.filter((field) => hasValue(payload[field])).length
            + (hasInvoice && manualInvoiceSide === "debit" ? 1 : 0)
        const creditCount = manualCreditFields.filter((field) => hasValue(payload[field])).length
            + (hasInvoice && manualInvoiceSide === "credit" ? 1 : 0)
        if (debitCount !== 1 || creditCount !== 1) {
            throw new Error("Für manuelle Buchungen muss genau ein Soll- und ein Haben-Konto ausgewählt werden")
        }

        payload.bankstatement = null
        payload.manualBookingDate = manualBookingDate
        if (hasInvoice) payload.manualInvoiceSide = manualInvoiceSide
    }

    if (bookingMode === "expense") return payload

    const depreciationMonths = requiredNumber(args, "depreciationMonths")
    const depreciationStartDate = stringArg(args, "depreciationStartDate")
    const depreciationMethod = stringArg(args, "depreciationMethod") || "linear"
    const residualValue = args.residualValue === undefined ? 0 : requiredNumber(args, "residualValue")

    if (!Number.isInteger(depreciationMonths) || depreciationMonths <= 0) {
        throw new Error("Die Abschreibungsdauer muss eine positive Anzahl Monate sein")
    }
    if (!validDate(depreciationStartDate)) throw new Error("Ein gültiger Abschreibungsbeginn ist erforderlich")
    if (!depreciationMethods.has(depreciationMethod)) {
        throw new Error(`Ungültige Abschreibungsmethode: ${depreciationMethod}`)
    }
    if (residualValue < 0) throw new Error("Der Restwert darf nicht negativ sein")

    payload.depreciationMonths = depreciationMonths
    payload.depreciationStartDate = depreciationStartDate
    payload.depreciationMethod = depreciationMethod
    if (args.depreciationLabel !== undefined) payload.depreciationLabel = stringArg(args, "depreciationLabel")
    payload.depreciationGroup = bookingMode === "depreciation_bundle" ? stringArg(args, "depreciationGroup") : null
    payload.residualValue = residualValue

    if (bookingMode === "depreciation_bundle" && !payload.depreciationGroup) {
        throw new Error("Für eine Sammelabschreibung ist eine Abschreibungsgruppe erforderlich")
    }

    return payload
}