package main

import (
	"bytes"
	"encoding/json"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/cloudwego/eino/schema"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

var testTime = time.Date(2026, time.May, 23, 12, 0, 0, 0, time.UTC)

// testFile creates an session jsonl file with the appropriate SessionHeader starting
// line.
func testFile(t *testing.T, dir string) (string, string) {
	t.Helper()
	f, err := os.CreateTemp(dir, "test-session-*.jsonl")
	if err != nil {
		// Panic risk in call to f.Name() if in error because f would be nil
		// t.Fatalf("failed to create temp session file %s", f.Name())
		t.Fatal("failed to create temp session file")
	}

	fullPath := f.Name()
	// Ensure files are cleaned up
	t.Cleanup(func() {
		_ = os.Remove(fullPath)
	})

	// os.File name can contain either the full path or the base file name
	// depending on what the Open method arguments are. The use of filepath.Base
	// ensures we only take the file name.
	id := strings.TrimSuffix(filepath.Base(fullPath), ".jsonl")

	s := SessionHeader{Type: "session", ID: id, CreatedAt: testTime}
	hData, err := json.Marshal(s)
	if err != nil {
		t.Fatalf("failed to marshal header data for %s", fullPath)
	}

	hData = append(hData, '\n')
	_, err = f.Write(hData)
	if err != nil {
		f.Close()
		t.Fatalf("failed to write session header to %s", fullPath)
	}

	if err = f.Close(); err != nil {
		t.Fatalf("failed to close test file %s", fullPath)
	}

	return fullPath, id
}

func TestSessionAppend(t *testing.T) {
	td := t.TempDir()
	fp, id := testFile(t, td)
	want := "Tell me about eino"

	s := Session{ID: id, CreatedAt: testTime, FilePath: fp}

	s.Append(&schema.Message{Role: schema.User, Content: want})

	var msg *schema.Message
	data, err := os.ReadFile(fp)
	assert.NoError(t, err)
	content := bytes.Split(data, []byte("\n"))
	rawMsg := bytes.TrimSpace(content[1]) // possible out of index if Append failed
	json.Unmarshal(rawMsg, &msg)          // didn't check parse error
	// we should convert to require which better documents the intention of the
	// code and the test
	assert.Equal(t, msg.Content, s.Messages[0].Content)

}

func TestSessionAppendBetter(t *testing.T) {
	td := os.TempDir()
	fp, id := testFile(t, td)
	want := "Tell me about eino"
	s := Session{ID: id, CreatedAt: testTime, FilePath: fp}

	err := s.Append(&schema.Message{Role: schema.User, Content: want})
	require.NoError(t, err, "s.Append should not return an error")

	data, err := os.ReadFile(s.FilePath)
	require.NoError(t, err, "failed to read from session file")
	// remove possible trailing newline in file contents
	data = bytes.TrimSpace(data)
	content := bytes.Split(data, []byte("\n"))
	require.Len(t, content, 2, "files should contain two lines")

	var msg *schema.Message
	err = json.Unmarshal(content[1], &msg)
	require.NoError(t, err, "content should json parse as eino Message")

	require.Equal(t, want, msg.Content, "retrieved message content should match test content")
	require.Len(t, s.Messages, 1, "session message should have 1 item")
	require.Equal(t, want, s.Messages[0].Content, "in memory content should match test content")

}