package eu.brassepc.fitnessdroid.data

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import kotlinx.serialization.json.Json
import kotlinx.serialization.json.JsonObject
import kotlinx.serialization.json.buildJsonObject
import kotlinx.serialization.json.jsonArray
import kotlinx.serialization.json.jsonObject
import kotlinx.serialization.json.jsonPrimitive
import kotlinx.serialization.json.put
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.RequestBody.Companion.toRequestBody
import java.util.concurrent.TimeUnit

class GraphQlException(val messages: List<String>) : Exception(messages.joinToString("; "))

/**
 * Minimal GraphQL-klient över OkHttp. Samma request-form som webbklienten
 * (gymTrackerApi.js): POST {query, variables} + "Authorization: Bearer <jwt>".
 */
class GraphQlClient(private val urlProvider: suspend () -> String) {

    private val http = OkHttpClient.Builder()
        .connectTimeout(10, TimeUnit.SECONDS)
        .readTimeout(30, TimeUnit.SECONDS)
        .build()

    val json = Json { ignoreUnknownKeys = true }

    suspend fun execute(
        query: String,
        variables: JsonObject = buildJsonObject {},
        token: String? = null,
    ): JsonObject = withContext(Dispatchers.IO) {
        val body = buildJsonObject {
            put("query", query)
            put("variables", variables)
        }
        val request = Request.Builder()
            .url(urlProvider())
            .post(body.toString().toRequestBody("application/json".toMediaType()))
            .apply { if (token != null) header("Authorization", "Bearer $token") }
            .build()

        http.newCall(request).execute().use { response ->
            val text = response.body?.string().orEmpty()
            // 5xx = servern/proxyn nere — behandla som nätfel (retry) och inte
            // som ett logiskt API-fel (som t.ex. loggar ut användaren).
            if (response.code >= 500) {
                throw java.io.IOException("HTTP ${response.code} från servern")
            }
            val root = runCatching { json.parseToJsonElement(text).jsonObject }.getOrNull()
                ?: throw GraphQlException(listOf("HTTP ${response.code}: oväntat svar från servern"))

            root["errors"]?.jsonArray?.takeIf { it.isNotEmpty() }?.let { errors ->
                throw GraphQlException(
                    errors.map {
                        it.jsonObject["message"]?.jsonPrimitive?.content ?: "Okänt fel"
                    }
                )
            }
            root["data"]?.jsonObject
                ?: throw GraphQlException(listOf("HTTP ${response.code}: tomt svar från servern"))
        }
    }
}