package com.sptmobile.pairing

import kotlinx.serialization.Serializable
import kotlinx.serialization.encodeToString
import kotlinx.serialization.json.Json

// [impl->REQ-GATEWAY-PERIPHERAL]
/**
 * The pairing payload the host prints as a QR code (`spt-mobile-host
 * pair-code`): version, iroh node key to dial, the Mobile Gateway endpoint id
 * being paired with, and the bearer token. Wire shape is owned by
 * `rust/link-proto` (`QrPayload`) — field names here must match it exactly,
 * because [toWireJson] re-encodes for `LinkNative.connect`.
 *
 * W2 entry path is manual paste (APP-PLAN Q1), so [parse] is defensive about
 * user-mangled input: surrounding whitespace is tolerated, every failure mode
 * returns a message fit for the pairing screen, and nothing throws.
 */
@Serializable
data class QrPayload(
    val v: Int,
    val node: String,
    val endpoint: String,
    val token: String,
) {
    /** Canonical JSON for the JNI seam (`LinkNative.connect`). */
    fun toWireJson(): String = json.encodeToString(this)

    companion object {
        /** The only payload version this app understands. */
        const val SUPPORTED_VERSION = 1

        private val json = Json { ignoreUnknownKeys = true }

        sealed interface ParseResult {
            data class Ok(val payload: QrPayload) : ParseResult
            data class Err(val message: String) : ParseResult
        }

        fun parse(text: String): ParseResult {
            val trimmed = text.trim()
            if (trimmed.isEmpty()) return ParseResult.Err("paste the host's pair-code JSON")
            val payload = try {
                json.decodeFromString<QrPayload>(trimmed)
            } catch (e: IllegalArgumentException) {
                return ParseResult.Err("not a pair-code payload: ${e.message}")
            }
            if (payload.v != SUPPORTED_VERSION) {
                return ParseResult.Err(
                    "unsupported pair-code version ${payload.v} (this app speaks v$SUPPORTED_VERSION)"
                )
            }
            if (payload.node.isBlank()) return ParseResult.Err("pair-code is missing the node key")
            if (payload.endpoint.isBlank()) return ParseResult.Err("pair-code is missing the endpoint id")
            if (payload.token.isBlank()) return ParseResult.Err("pair-code is missing the token")
            return ParseResult.Ok(payload)
        }
    }
}