package main

import (
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

// subagentTestFullContext is the error body of a call whose input does not fit
// in the context of the model.
const subagentTestFullContext = `{"error": {"message": "Your input exceeds the context window of this model.", "type": "invalid_request_error", "code": "context_length_exceeded"}}`

func TestSpawnRunsASubagentInTheBackground(t *testing.T) {
	server := newModelFake(t)
	var test *TurnTestLoop
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		last := subagentTestLastItem(call)
		switch {
		case subagentTestCall(call) && last["type"] == "function_call_output":
			// The report comes after the reply of the turn of the spawn.
			test.events.WaitFor(t, "reply", 1)
			modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("There are 3 files.")}, 100, 0, 5))
		case subagentTestCall(call):
			modelWriteEvents(w, modelCompletedEvent([]any{modelFunctionCallItem("fc_1", "call_1", "shell", `{"command":"pwd"}`)}, 100, 0, 5))
		case last["type"] == "function_call_output":
			modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("Started.")}, 100, 0, 5))
		case strings.HasPrefix(subagentTestText(last), "["):
			modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("Noted.")}, 100, 0, 5))
		default:
			modelWriteEvents(w, modelCompletedEvent([]any{modelFunctionCallItem("fc_1", "call_1", "spawn", `{"tasks":["Count the files."],"effort":null}`)}, 100, 0, 5))
		}
	}

	test = newTestTurnLoop(t, server)
	_, err := test.loop.Submit(terminalSource, "Count the files in a subagent.")
	require.NoError(t, err)
	test.events.WaitFor(t, "idle", 2)

	name := test.events.Last("subagent")
	require.True(t, subagentNameValid(name), name)
	work := filepath.Join(test.loop.runs.subagents.dir, name, "work")
	require.DirExists(t, work)

	report := "[" + name + "]\nThere are 3 files.\n\nFull chat: zoom(\"" + name + "\")"
	require.Equal(t, []string{
		"user: Count the files in a subagent.",
		`tool: spawn {"tasks":["Count the files."],"effort":null}`,
		"echo: Started " + name + ". Each one's report will reach you as a message when it finishes.",
		"reply: Started.",
		"work: " + report,
		"reply: Noted.",
	}, test.Log(t))

	var first, second *ModelFakeCall
	for n := range server.Calls() {
		call := server.Call(n)
		if !subagentTestCall(call) {
			continue
		}

		if first == nil {
			first = &call
		} else {
			second = &call
		}
	}

	require.NotNil(t, second)

	// The first request of the subagent holds the view, the state, and its
	// whole log, with its own prompt and tools.
	texts := turnInputTexts(t, *first)
	view := strings.Join(texts[:len(texts)-2], "")
	require.True(t, strings.HasPrefix(view, "<chat>\n0+1|user: Count the files in a subagent.\n1+1|tool: spawn"), view)
	require.Equal(t, "</chat>\n\nNow: Thursday 2026-01-01 12:00 +00:00", texts[len(texts)-2])
	require.Equal(t, "0|note: subagent\n\n1|user: Count the files.", texts[len(texts)-1])

	instructions, err := test.agent.SubagentPrompt()
	require.NoError(t, err)
	require.Equal(t, instructions, first.body["instructions"])

	var tools []string
	for _, tool := range first.body["tools"].([]any) {
		tools = append(tools, tool.(map[string]any)["name"].(string))
	}

	require.Equal(t, []string{"zoom", "date", "shell", "read", "write", "edit"}, tools)
	require.Equal(t, work+"\n", subagentTestLastItem(*second)["output"])

	subagent, err := test.loop.runs.subagents.Get(t.Context(), name)
	require.NoError(t, err)

	log, err := subagent.Show()
	require.NoError(t, err)
	require.Equal(t, "0|note: subagent\n\n1|user: Count the files.\n\n2|tool: shell {\"command\":\"pwd\"}\n\n3|echo: "+work+"\n\n\n4|reply: There are 3 files.", log)

	var agents []string
	for _, record := range modelReadUsage(t, test.usagePath) {
		agents = append(agents, record.Agent)
	}

	require.ElementsMatch(t, []string{"", "", "", name, name}, agents)
}

func TestReportJoinsTheNextRequestOfARunningTurn(t *testing.T) {
	server := newModelFake(t)
	arrived := make(chan struct{})
	release := make(chan struct{})
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		if call.number == 0 {
			close(arrived)
			<-release
			modelWriteEvents(w, modelCompletedEvent([]any{modelFunctionCallItem("fc_1", "call_1", "date", `{"id":0}`)}, 100, 0, 5))

			return
		}

		modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("done")}, 100, 0, 5))
	}

	test := newTestTurnLoop(t, server)
	_, err := test.loop.Submit(terminalSource, "first")
	require.NoError(t, err)

	<-arrived
	report := subagentReport("GreenOtter", []string{"It is done."})
	test.loop.Report(report, false)
	close(release)

	test.events.WaitFor(t, "idle", 1)
	require.Equal(t, report, subagentTestText(subagentTestLastItem(server.Call(1))))

	time.Sleep(50 * time.Millisecond)
	require.Equal(t, 2, server.Calls())
	require.Equal(t, 1, test.events.Count("busy"))
}

func TestReportOfAStoppedSubagentStartsNoTurn(t *testing.T) {
	server := newModelFake(t)
	test := newTestTurnLoop(t, server)
	report := subagentReport("GreenOtter", []string{"failed: context canceled"})
	test.loop.Report(report, true)

	test.events.WaitFor(t, "work", 1)
	time.Sleep(50 * time.Millisecond)
	require.Equal(t, []string{"work: " + report}, test.Log(t))
	require.Zero(t, server.Calls())
	require.Zero(t, test.events.Count("busy"))
}

func TestFullContextGivesAFailedReport(t *testing.T) {
	server := newModelFake(t)
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		if subagentTestCall(call) {
			w.WriteHeader(http.StatusBadRequest)
			_, _ = io.WriteString(w, subagentTestFullContext)

			return
		}

		modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("It failed.")}, 100, 0, 5))
	}

	test := newTestTurnLoop(t, server)
	_, err := test.loop.runs.Spawn(t.Context(), []string{"Read the big file."}, nil)
	require.NoError(t, err)
	test.events.WaitFor(t, "idle", 1)

	name := test.events.Last("subagent")
	require.Equal(t, []string{
		"work: [" + name + "]\nfailed: model call: HTTP 400: " + subagentTestFullContext + "\n\nFull chat: zoom(\"" + name + "\")",
		"reply: It failed.",
	}, test.Log(t))
}

func TestSubagentHasItsOwnEffortAndNoSpawn(t *testing.T) {
	server := newModelFake(t)
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		if subagentTestCall(call) && subagentTestLastItem(call)["type"] != "function_call_output" {
			modelWriteEvents(w, modelCompletedEvent([]any{modelFunctionCallItem("fc_1", "call_1", "spawn", `{"tasks":["More."],"effort":null}`)}, 100, 0, 5))

			return
		}

		modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("ok")}, 100, 0, 5))
	}

	test := newTestTurnLoop(t, server)
	runs := test.loop.runs
	_, err := runs.Spawn(t.Context(), nil, nil)
	require.EqualError(t, err, "no tasks")

	effort := "max"
	_, err = runs.Spawn(t.Context(), []string{"Think."}, &effort)
	require.EqualError(t, err, `no effort "max": one of low, medium, high, xhigh`)

	effort = "high"
	_, err = runs.Spawn(t.Context(), []string{"Think hard."}, &effort)
	require.NoError(t, err)
	test.events.WaitFor(t, "idle", 1)

	for n := range server.Calls() {
		call := server.Call(n)
		if subagentTestCall(call) {
			require.Equal(t, "high", call.body["reasoning"].(map[string]any)["effort"])
		}
	}

	subagent, err := runs.subagents.Get(t.Context(), test.events.Last("subagent"))
	require.NoError(t, err)

	log, err := subagent.Show()
	require.NoError(t, err)
	require.Equal(t, "0|note: subagent at effort high\n\n1|user: Think hard.\n\n2|tool: spawn {\"tasks\":[\"More.\"],\"effort\":null}\n\n3|echo: error: unknown tool \"spawn\"\n\n4|reply: ok", log)

	entries, err := os.ReadDir(runs.subagents.dir)
	require.NoError(t, err)
	require.Len(t, entries, 1)
}

func TestCloseEndsTheSubagentsWithNoReport(t *testing.T) {
	server := newModelFake(t)
	arrived := make(chan struct{})
	release := make(chan struct{})
	t.Cleanup(func() {
		close(release)
	})

	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		close(arrived)
		<-release
	}

	test := newTestTurnLoop(t, server)
	runs := test.loop.runs
	_, err := runs.Spawn(t.Context(), []string{"Wait."}, nil)
	require.NoError(t, err)

	<-arrived
	runs.Close()
	require.Empty(t, runs.running)
	require.Empty(t, test.Log(t))

	_, err = runs.Spawn(t.Context(), []string{"Again."}, nil)
	require.ErrorIs(t, err, errSubagentClosed)

	entries, err := os.ReadDir(runs.subagents.dir)
	require.NoError(t, err)
	require.Len(t, entries, 1)
}

// subagentTestCall tells if call is a call of a subagent.
func subagentTestCall(call ModelFakeCall) bool {
	instructions, _ := call.body["instructions"].(string)

	return strings.HasPrefix(instructions, "You are a subagent")
}

// subagentTestLastItem returns the last input item of call.
func subagentTestLastItem(call ModelFakeCall) map[string]any {
	input := call.body["input"].([]any)

	return input[len(input)-1].(map[string]any)
}

// subagentTestText returns the text of the user message item, or "" for
// another item.
func subagentTestText(item map[string]any) string {
	content, _ := item["content"].([]any)
	var text strings.Builder
	for _, part := range content {
		value, _ := part.(map[string]any)["text"].(string)
		text.WriteString(value)
	}

	return text.String()
}