import { timingSafeEqual } from "crypto"
import {
    getEnvFallback,
    getValueSource,
    isSettingsWritable,
    loadSettings,
    saveSettings,
} from "@/lib/admin/settings"
import {
    SETTINGS_BY_KEY,
    SETTINGS_REGISTRY,
    type SettingDef,
} from "@/lib/admin/settings-registry"
import { ServerModelsConfigSchema } from "@/lib/server-model-config"

// Zod schemas for json-type settings (kept here, server-side only — the
// registry is imported by the client and must stay free of server deps)
const JSON_VALIDATORS: Record<string, typeof ServerModelsConfigSchema> = {
    AI_MODELS_CONFIG: ServerModelsConfigSchema,
}

export const runtime = "nodejs"
export const dynamic = "force-dynamic"

function checkAuth(req: Request): Response | null {
    const password = process.env.ADMIN_PASSWORD
    if (!password) {
        return Response.json(
            {
                error: "Admin panel is disabled. Set the ADMIN_PASSWORD environment variable to enable it.",
            },
            { status: 403 },
        )
    }
    const provided = req.headers.get("x-admin-password") || ""
    const a = Buffer.from(provided)
    const b = Buffer.from(password)
    if (a.length !== b.length || !timingSafeEqual(a, b)) {
        return Response.json(
            { error: "Invalid admin password" },
            { status: 401 },
        )
    }
    return null
}

function maskSecret(value: string): { isSet: true; hint: string } {
    return {
        isSet: true,
        hint: value.length > 8 ? `…${value.slice(-4)}` : "••••",
    }
}

function serializeSettings() {
    const fileValues = loadSettings()
    return SETTINGS_REGISTRY.map((def) => {
        const source = getValueSource(def.key)
        const raw =
            source === "file"
                ? fileValues[def.key]
                : (getEnvFallback(def.key) ?? null)
        const value = def.type === "secret" && raw ? maskSecret(raw) : raw
        return { key: def.key, source, value }
    })
}

export async function GET(req: Request) {
    const authError = checkAuth(req)
    if (authError) return authError

    return Response.json({
        writable: isSettingsWritable(),
        settings: serializeSettings(),
    })
}

function validateValue(def: SettingDef, value: string): string | null {
    switch (def.type) {
        case "number": {
            const num = Number(value)
            if (Number.isNaN(num)) return "Must be a number"
            if (def.min !== undefined && num < def.min)
                return `Must be at least ${def.min}`
            if (def.max !== undefined && num > def.max)
                return `Must be at most ${def.max}`
            return null
        }
        case "boolean":
            return value === "true" || value === "false"
                ? null
                : 'Must be "true" or "false"'
        case "enum":
            return def.options?.includes(value)
                ? null
                : `Must be one of: ${def.options?.join(", ")}`
        case "json": {
            let parsed: unknown
            try {
                parsed = JSON.parse(value)
            } catch {
                return "Invalid JSON"
            }
            const schema = JSON_VALIDATORS[def.key]
            if (schema) {
                const result = schema.safeParse(parsed)
                if (!result.success) {
                    return `Invalid value: ${result.error.issues[0]?.message ?? "schema mismatch"}`
                }
            }
            return null
        }
        default:
            return null
    }
}

export async function PUT(req: Request) {
    const authError = checkAuth(req)
    if (authError) return authError

    if (!isSettingsWritable()) {
        return Response.json(
            {
                error: "Settings file is not writable on this deployment. Configure via environment variables instead.",
            },
            { status: 503 },
        )
    }

    let body: { values?: Record<string, unknown> }
    try {
        body = await req.json()
    } catch {
        return Response.json({ error: "Invalid JSON body" }, { status: 400 })
    }
    if (!body.values || typeof body.values !== "object") {
        return Response.json(
            { error: "Body must contain a values object" },
            { status: 400 },
        )
    }

    const updates: Record<string, string | null> = {}
    const errors: Record<string, string> = {}

    for (const [key, value] of Object.entries(body.values)) {
        const def = SETTINGS_BY_KEY.get(key)
        if (!def) {
            errors[key] = "Unknown setting"
            continue
        }
        if (value === null || value === "") {
            updates[key] = null
            continue
        }
        if (typeof value !== "string") {
            errors[key] = "Value must be a string"
            continue
        }
        const error = validateValue(def, value)
        if (error) {
            errors[key] = error
            continue
        }
        updates[key] = value
    }

    if (Object.keys(errors).length > 0) {
        return Response.json({ errors }, { status: 400 })
    }

    saveSettings(updates)

    return Response.json({
        writable: true,
        settings: serializeSettings(),
    })
}