package main

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"testing"
	"time"
)

func writeJSONL(t *testing.T, path string, messages []JSONLMessage) {
	t.Helper()
	f, err := os.Create(path)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()

	enc := json.NewEncoder(f)
	for _, msg := range messages {
		if err := enc.Encode(msg); err != nil {
			t.Fatal(err)
		}
	}
}

func makeMessages(n int) []JSONLMessage {
	msgs := make([]JSONLMessage, n)
	for i := range msgs {
		msgs[i] = JSONLMessage{
			Type:      "assistant",
			Timestamp: time.Now().UTC().Format(time.RFC3339),
			SessionID: "test-session",
			Cwd:       "/tmp",
			GitBranch: "main",
			Message: &MessagePayload{
				Role:       "assistant",
				Content:    []ContentBlock{{Type: "text", Text: fmt.Sprintf("line %d", i+1)}},
				StopReason: "end_turn",
			},
		}
	}
	return msgs
}

func TestTailReadJSONL(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "test.jsonl")
	writeJSONL(t, path, makeMessages(50))

	msgs, err := TailReadJSONL(path, 3)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if len(msgs) != 3 {
		t.Fatalf("expected 3 messages, got %d", len(msgs))
	}
	// Should be the last 3 (chronological order: 48, 49, 50)
	if msgs[0].Message.Content[0].Text != "line 48" {
		t.Errorf("first message text = %q, want %q", msgs[0].Message.Content[0].Text, "line 48")
	}
	if msgs[2].Message.Content[0].Text != "line 50" {
		t.Errorf("last message text = %q, want %q", msgs[2].Message.Content[0].Text, "line 50")
	}
}

func TestTailReadJSONL_TruncatedLastLine(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "test.jsonl")

	// Write 5 complete lines then a truncated line (no trailing \n)
	writeJSONL(t, path, makeMessages(5))

	// Append truncated JSON (no newline)
	f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0o644)
	if err != nil {
		t.Fatal(err)
	}
	f.WriteString(`{"type":"assistant","timestamp":"2026-01-01T00:00:00Z"`)
	f.Close()

	msgs, err := TailReadJSONL(path, 3)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if len(msgs) != 3 {
		t.Fatalf("expected 3 messages (truncated ignored), got %d", len(msgs))
	}
	// Last complete line should be line 5
	if msgs[2].Message.Content[0].Text != "line 5" {
		t.Errorf("last message text = %q, want %q", msgs[2].Message.Content[0].Text, "line 5")
	}
}

func TestTailReadJSONL_EmptyFile(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "empty.jsonl")
	os.WriteFile(path, []byte{}, 0o644)

	msgs, err := TailReadJSONL(path, 3)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if len(msgs) != 0 {
		t.Errorf("expected 0 messages for empty file, got %d", len(msgs))
	}
}

func TestTailReadJSONL_SmallFile(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "small.jsonl")
	writeJSONL(t, path, makeMessages(2))

	msgs, err := TailReadJSONL(path, 10)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if len(msgs) != 2 {
		t.Fatalf("expected 2 messages, got %d", len(msgs))
	}
}

func TestFindSessionForProcess(t *testing.T) {
	dir := t.TempDir()
	cwd := "/home/user/my-project"
	encoded := EncodePath(cwd)
	projectDir := filepath.Join(dir, encoded)
	os.MkdirAll(projectDir, 0o755)

	// Create two JSONL files with different mtimes
	older := filepath.Join(projectDir, "old-session.jsonl")
	newer := filepath.Join(projectDir, "new-session.jsonl")

	olderMsgs := []JSONLMessage{{
		Type: "assistant", Timestamp: "2026-03-22T10:00:00Z",
		SessionID: "old-id", Cwd: cwd, GitBranch: "old-branch",
		Message: &MessagePayload{Role: "assistant", Content: []ContentBlock{{Type: "text", Text: "old"}}, StopReason: "end_turn"},
	}}
	newerMsgs := []JSONLMessage{{
		Type: "assistant", Timestamp: "2026-03-23T12:00:00Z",
		SessionID: "new-id", Cwd: cwd, GitBranch: "feat-x",
		Message: &MessagePayload{Role: "assistant", Content: []ContentBlock{{Type: "text", Text: "new"}}, StopReason: "end_turn"},
	}}

	writeJSONL(t, older, olderMsgs)
	// Ensure newer has a later mtime
	time.Sleep(10 * time.Millisecond)
	writeJSONL(t, newer, newerMsgs)

	proc := Process{PID: 42, Cwd: cwd}
	jsonlPath, msgs, err := FindSessionForProcess(dir, proc)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if jsonlPath != newer {
		t.Errorf("expected newest JSONL %q, got %q", newer, jsonlPath)
	}
	if len(msgs) == 0 {
		t.Fatal("expected at least 1 message")
	}
	if msgs[0].SessionID != "new-id" {
		t.Errorf("sessionID = %q, want %q", msgs[0].SessionID, "new-id")
	}
}

func TestFindSessionForProcess_NoMatch(t *testing.T) {
	dir := t.TempDir()
	proc := Process{PID: 42, Cwd: "/nonexistent/path"}

	_, _, err := FindSessionForProcess(dir, proc)
	if err == nil {
		t.Fatal("expected error for no matching JSONL, got nil")
	}
}

func TestFindSessionForProcess_ExcludesSubagents(t *testing.T) {
	dir := t.TempDir()
	cwd := "/home/user/project"
	encoded := EncodePath(cwd)
	projectDir := filepath.Join(dir, encoded)
	os.MkdirAll(projectDir, 0o755)

	// Create a main session JSONL
	mainJSONL := filepath.Join(projectDir, "main-session.jsonl")
	writeJSONL(t, mainJSONL, []JSONLMessage{{
		Type: "assistant", Timestamp: "2026-03-23T12:00:00Z",
		SessionID: "main-id", Cwd: cwd, GitBranch: "main",
		Message: &MessagePayload{Role: "assistant", Content: []ContentBlock{{Type: "text", Text: "main"}}, StopReason: "end_turn"},
	}})

	// Create a subagent JSONL in a subdirectory (should be excluded)
	subDir := filepath.Join(projectDir, "some-uuid", "subagents")
	os.MkdirAll(subDir, 0o755)
	subJSONL := filepath.Join(subDir, "agent-1.jsonl")
	writeJSONL(t, subJSONL, []JSONLMessage{{
		Type: "assistant", Timestamp: "2026-03-23T13:00:00Z",
		SessionID: "sub-id", Cwd: cwd, GitBranch: "main",
		Message: &MessagePayload{Role: "assistant", Content: []ContentBlock{{Type: "text", Text: "sub"}}, StopReason: "end_turn"},
	}})

	proc := Process{PID: 42, Cwd: cwd}
	jsonlPath, msgs, err := FindSessionForProcess(dir, proc)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if jsonlPath != mainJSONL {
		t.Errorf("expected main JSONL %q, got %q", mainJSONL, jsonlPath)
	}
	if msgs[0].SessionID != "main-id" {
		t.Errorf("should use main session, got sessionID=%q", msgs[0].SessionID)
	}
}