package com.sptmobile.link

import org.junit.Assert.assertEquals
import org.junit.Assert.assertTrue
import org.junit.Test

// [unit->REQ-DEVICE-LINK-IROH]
// Pins the Kotlin side of the followNext envelope contract
// (rust/link-android/src/lib.rs module doc): the closed delta/timeout/end/error
// set decodes exactly, and nothing an envelope can contain crashes the reader
// loop.
class FollowEventTest {
    @Test
    fun `delta carries the raw delta line verbatim`() {
        val delta = """{"version":1,"from":3,"turns":[{"seq":4}]}"""
        val event = FollowEvent.decode(
            """{"event":"delta","delta":"{\"version\":1,\"from\":3,\"turns\":[{\"seq\":4}]}"}"""
        )
        assertEquals(FollowEvent.Delta(delta), event)
    }

    @Test
    fun `timeout and end decode to their singletons`() {
        assertEquals(FollowEvent.Timeout, FollowEvent.decode("""{"event":"timeout"}"""))
        assertEquals(FollowEvent.End, FollowEvent.decode("""{"event":"end"}"""))
    }

    @Test
    fun `error carries the message`() {
        assertEquals(
            FollowEvent.Error("link dropped"),
            FollowEvent.decode("""{"event":"error","message":"link dropped"}""")
        )
    }

    @Test
    fun `error without message still decodes`() {
        assertEquals(
            FollowEvent.Error("unknown stream error"),
            FollowEvent.decode("""{"event":"error"}""")
        )
    }

    @Test
    fun `unknown event becomes Error not a crash`() {
        val event = FollowEvent.decode("""{"event":"upgrade-v2"}""")
        assertTrue(event is FollowEvent.Error)
    }

    @Test
    fun `malformed json becomes Error not a crash`() {
        assertTrue(FollowEvent.decode("not json at all") is FollowEvent.Error)
        assertTrue(FollowEvent.decode("""{"delta":"x"}""") is FollowEvent.Error)
    }

    @Test
    fun `delta envelope missing its delta field becomes Error`() {
        assertTrue(FollowEvent.decode("""{"event":"delta"}""") is FollowEvent.Error)
    }

    @Test
    fun `unknown extra keys are tolerated`() {
        assertEquals(
            FollowEvent.Timeout,
            FollowEvent.decode("""{"event":"timeout","extra":42}""")
        )
    }
}