package main

import (
	"encoding/json"
	"io"
	"net/http"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
	"unicode/utf8"

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

func TestCompactorSendsThePromptToolsAndTask(t *testing.T) {
	server := newModelFake(t)
	compactor := newTestCompactor(t, server)

	line, err := compactor.Summarize(t.Context(), Task{
		Level:   0,
		Index:   7,
		Context: "<chat>\n0+4|user: earlier\n</chat>",
		Input:   []string{"user: " + strings.Repeat("x", 600)},
	})
	require.NoError(t, err)
	require.Equal(t, "a line", line)
	require.Equal(t, 1, server.Calls())

	body := server.Call(0).body
	require.Equal(t, prompt("Ada", "/AGENT/instructions.md", ""), body["instructions"])
	require.Equal(t, "gpt-test", body["model"])
	require.Equal(t, map[string]any{"effort": "high"}, body["reasoning"])
	require.Equal(t, "agent-key", body["prompt_cache_key"])

	tools, err := json.Marshal(promptTools())
	require.NoError(t, err)

	sent, err := json.Marshal(body["tools"])
	require.NoError(t, err)
	require.JSONEq(t, string(tools), string(sent))

	texts := compactorInputTexts(t, server.Call(0))
	require.Equal(t, []string{
		"<chat>\n0+4|user: earlier\n</chat>\n" +
			"Compaction: compress message 7 into one line of at most 512 bytes\n" +
			"(about 70 words), the length of this ruler:\n" +
			strings.Repeat("-", 512) + "\n" +
			"<input>\nuser: " + strings.Repeat("x", 600) + "\n</input>",
	}, texts)
}

func TestCompactorWritesTheMergeTask(t *testing.T) {
	text, err := compactorTask(Task{
		Level: 2,
		Index: 3,
		Input: []string{"left line", "right line"},
	})
	require.NoError(t, err)
	require.Equal(t, "Compaction: merge lines 12+2 and 14+2, adjacent, into one line of at most\n"+
		"512 bytes (about 70 words), the length of this ruler:\n"+
		strings.Repeat("-", 512)+"\n"+
		"<chat> may hold their messages, 12 to 15, in more detail: take details\n"+
		"of them from there too.\n"+
		"<input>\nleft line\nright line\n</input>", text)
}

func TestCompactorRetriesALongLineWithTheNewestNote(t *testing.T) {
	long := []string{strings.Repeat("a", 600), strings.Repeat("b", 550), strings.Repeat("c", 400)}
	server := newModelFake(t)
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem(long[call.number])}, 100, 0, 5))
	}

	task := compactorLeafTask()
	task.Context = "<chat>\n0+1|a\n1+1|b\n2+1|c\n3+1|d\n4+1|e\n</chat>"

	compactor := newTestCompactor(t, server)
	line, err := compactor.Summarize(t.Context(), task)
	require.NoError(t, err)
	require.Equal(t, long[2], line)
	require.Equal(t, 3, server.Calls())

	records := modelReadUsage(t, compactor.client.usage.path)
	require.Len(t, records, 3)

	for n, record := range records {
		require.Equal(t, &[2]int{0, 0}, record.Node)
		require.Equal(t, len(long[n]), record.TextBytes)
	}

	text, err := compactorTask(task)
	require.NoError(t, err)

	first := compactorInputTexts(t, server.Call(0))
	require.Equal(t, []string{task.Context + "\n" + text}, first)

	for n, want := range []string{long[0], long[1]} {
		call := server.Call(n + 1)
		texts := compactorInputTexts(t, call)
		require.Equal(t, first, texts[:1])
		require.Equal(t, []string{compactorTooLong(want)}, texts[1:])
		require.Contains(t, texts[1], "was "+strconv.Itoa(len(want))+" bytes,")
		require.Contains(t, texts[1], "\n"+want[:512]+"| <- LIMIT")

		note, err := json.Marshal(modelUserMessage(texts[1]))
		require.NoError(t, err)
		require.LessOrEqual(t, len(call.raw), len(server.Call(0).raw)+len(",")+len(note))
	}
}

func TestCompactorKeepsTheShortestOfFiveLines(t *testing.T) {
	sizes := []int{700, 530, 600, 520, 560, 513}
	server := newModelFake(t)
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem(strings.Repeat("z", sizes[call.number]))}, 100, 0, 5))
	}

	line, err := newTestCompactor(t, server).Summarize(t.Context(), compactorLeafTask())
	require.NoError(t, err)
	require.Equal(t, compactorTries, server.Calls())
	require.Len(t, line, 520)
}

func TestCompactorFailsWithoutALine(t *testing.T) {
	testCases := []struct {
		name  string
		reply func(http.ResponseWriter, ModelFakeCall)
		want  string
	}{
		{
			name: "failed call",
			reply: func(w http.ResponseWriter, _ ModelFakeCall) {
				w.WriteHeader(http.StatusInternalServerError)

				_, _ = io.WriteString(w, "down")
			},
			want: "HTTP 500",
		},
		{
			name: "tool call and no text",
			reply: func(w http.ResponseWriter, _ ModelFakeCall) {
				modelWriteEvents(w, modelCompletedEvent([]any{map[string]any{"type": "function_call", "name": "zoom", "arguments": "{}"}}, 100, 0, 5))
			},
			want: "no line",
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			server := newModelFake(t)
			server.reply = tc.reply

			_, err := newTestCompactor(t, server).Summarize(t.Context(), compactorLeafTask())
			require.ErrorContains(t, err, tc.want)
			require.Equal(t, 1, server.Calls())
		})
	}
}

func TestCutLineKeepsWholeCharacters(t *testing.T) {
	line := strings.Repeat("a", 511) + "é" + "tail"
	cut := compactorCutLine(line)
	require.Equal(t, strings.Repeat("a", 511), cut)
	require.True(t, utf8.ValidString(cut))
	require.Equal(t, "short", compactorCutLine("short"))
}

func TestCompactorBuildsNodesInTheCore(t *testing.T) {
	server := newModelFake(t)
	server.reply = func(w http.ResponseWriter, call ModelFakeCall) {
		if call.number == 0 {
			w.WriteHeader(http.StatusServiceUnavailable)

			return
		}

		modelWriteEvents(w, modelCompletedEvent([]any{modelMessageItem("summary of the long output")}, 100, 0, 5))
	}

	memory, err := openMemory(t.Context(), t.TempDir(), newTestClock().Now, newTestCompactor(t, server), discardLog())
	require.NoError(t, err)

	defer func() {
		require.NoError(t, memory.Close())
	}()

	_, err = memory.Append("echo", strings.Repeat("output ", 200))
	require.NoError(t, err)
	require.NoError(t, memory.Wait(t.Context()))
	require.False(t, treeIsBuilt(t, memory.tree, 0, 0))

	_, err = memory.Append("user", "next")
	require.NoError(t, err)
	require.NoError(t, memory.Wait(t.Context()))

	node := treeReadNode(t, memory.tree, 0, 0)
	require.Equal(t, "summary of the long output", node.Text)
	require.Equal(t, "<chat>\n0+1|summary of the long output\n1+1|user: next\n</chat>", memory.View())
	require.Equal(t, 2, server.Calls())
}

func newTestCompactor(t *testing.T, server *ModelFake) *Compactor {
	t.Helper()

	client := newModelClient(server.URL, ModelAPIKey(modelTestKey), "agent-key", filepath.Join(t.TempDir(), "usage.jsonl"))

	return newCompactor(client, compactorAdaPrompt, ModelConfig{
		Model:  "gpt-test",
		Effort: "high",
	}, promptTools())
}

// compactorInputTexts returns the text of each user message of call. Each
// message has one text part.
func compactorInputTexts(t *testing.T, call ModelFakeCall) []string {
	t.Helper()

	var body struct {
		Input []struct {
			Role    string `json:"role"`
			Content []struct {
				Type string `json:"type"`
				Text string `json:"text"`
			} `json:"content"`
		} `json:"input"`
	}

	require.NoError(t, json.Unmarshal(call.raw, &body))

	texts := make([]string, len(body.Input))
	for n, message := range body.Input {
		require.Equal(t, "user", message.Role)
		require.Len(t, message.Content, 1)
		require.Equal(t, "input_text", message.Content[0].Type)

		texts[n] = message.Content[0].Text
	}

	return texts
}

func compactorLeafTask() Task {
	return Task{
		Level:   0,
		Index:   0,
		Context: "<chat>\n</chat>",
		Input:   []string{"user: " + strings.Repeat("y", 600)},
	}
}

// compactorAdaPrompt returns the prompt of the agent Ada, without instructions.
func compactorAdaPrompt() (string, error) {
	return prompt("Ada", "/AGENT/instructions.md", ""), nil
}