File size: 23,341 Bytes
3d1636d
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
This section provides examples of writing chat UIs in Mesop. Each example is wrapped in <example> tags.

<example>
# This is an example of a basic chat app.
import random
import time
from dataclasses import dataclass
from typing import Literal

import mesop as me

Role = Literal["user", "bot"]


@dataclass(kw_only=True)
class ChatMessage:
  """Chat message metadata."""

  role: Role = "user"
  content: str = ""
  edited: bool = False


@me.stateclass
class State:
  input: str
  output: list[ChatMessage]
  in_progress: bool


@me.page()
def basic_chat():
  state = me.state(State)
  with me.box(
    style=me.Style(
      color=me.theme_var("on-surface"),
      background=me.theme_var("surface-container-lowest"),
      display="flex",
      flex_direction="column",
      height="100%",
      padding=me.Padding.all(15),
    )
  ):
    # This contains the chat messages that have been recorded. This takes 50fr.
    # This section can be replaced with other types of chat messages.

    # We set overflow to scroll so that the chat input will be fixed at the bottom.
    with me.box(style=me.Style(overflow_y="scroll", flex_grow=1)):
      for msg in state.output:
        # User chat message
        if msg.role == "user":
          with me.box(
            style=me.Style(display="flex", gap=15, margin=me.Margin.all(20))
          ):
            # User avatar/icon box
            me.text(
              "U",
              style=me.Style(
                background=me.theme_var("primary"),
                border_radius="50%",
                color=me.theme_var("on-primary"),
                font_size=20,
                height=40,
                width=40,
                text_align="center",
                line_height="1",
                padding=me.Padding(top=10),
                margin=me.Margin(top=16),
              ),
            )
            # User query
            me.markdown(msg.content)
        else:
          # Bot chat message
          with me.box(
            style=me.Style(display="flex", gap=15, margin=me.Margin.all(20))
          ):
            # Bot avatar/icon box
            me.text(
              "B",
              style=me.Style(
                background=me.theme_var("secondary"),
                border_radius="50%",
                color=me.theme_var("on-secondary"),
                font_size=20,
                height=40,
                width="40px",
                text_align="center",
                line_height="1",
                padding=me.Padding(top=10),
                margin=me.Margin(top=16),
              ),
            )
            # Bot message response
            me.markdown(
              msg.content,
              style=me.Style(color=me.theme_var("on-surface")),
            )

    # This is for the basic chat input. This is the second row at 1fr.
    # This section can be replaced with other types of chat inputs.
    with me.box(
      style=me.Style(
        border_radius=16,
        padding=me.Padding.all(8),
        background=me.theme_var("surface-container-low"),
        display="flex",
        width="100%",
      )
    ):
      with me.box(
        style=me.Style(
          flex_grow=1,
        )
      ):
        me.native_textarea(
          key="chat_input",
          value=state.input,
          on_blur=on_chat_input,
          autosize=True,
          min_rows=4,
          placeholder="Subtle chat input",
          style=me.Style(
            color=me.theme_var("on-surface-variant"),
            padding=me.Padding(top=16, left=16),
            background=me.theme_var("surface-container-low"),
            outline="none",
            width="100%",
            overflow_y="auto",
            border=me.Border.all(
              me.BorderSide(style="none"),
            ),
          ),
        )
      with me.content_button(
        type="icon",
        on_click=on_click_submit_chat_msg,
        # If we're processing a message prevent new queries from being sent
        disabled=state.in_progress,
      ):
        me.icon("send")


def on_chat_input(e: me.InputBlurEvent):
  """Capture chat text input on blur."""
  state = me.state(State)
  state.input = e.value


def on_click_submit_chat_msg(e: me.ClickEvent):
  """Handles submitting a chat message."""
  state = me.state(State)
  if state.in_progress or not state.input:
    return
  input = state.input
  # Clear the text input.
  state.input = ""
  yield

  output = state.output
  if output is None:
    output = []
  output.append(ChatMessage(role="user", content=input))
  state.in_progress = True
  yield

  start_time = time.time()
  # Send user input and chat history to get the bot response.
  output_message = respond_to_chat(input, state.output)
  assistant_message = ChatMessage(role="bot")
  output.append(assistant_message)
  state.output = output
  for content in output_message:
    assistant_message.content += content
    # TODO: 0.25 is an abitrary choice. In the future, consider making this adjustable.
    if (time.time() - start_time) >= 0.25:
      start_time = time.time()
      yield

  state.in_progress = False
  me.focus_component(key="chat_input")
  yield


def respond_to_chat(input: str, history: list[ChatMessage]):
  """Displays random canned text.

  Edit this function to process messages with a real chatbot/LLM.
  """
  lines = [
    "Mesop is a Python-based UI framework designed to simplify web UI development for engineers without frontend experience.",
    "It leverages the power of the Angular web framework and Angular Material components, allowing rapid construction of web demos and internal tools.",
    "With Mesop, developers can enjoy a fast build-edit-refresh loop thanks to its hot reload feature, making UI tweaks and component integration seamless.",
    "Deployment is straightforward, utilizing standard HTTP technologies.",
    "Mesop's component library aims for comprehensive Angular Material component coverage, enhancing UI flexibility and composability.",
    "It supports custom components for specific use cases, ensuring developers can extend its capabilities to fit their unique requirements.",
    "Mesop's roadmap includes expanding its component library and simplifying the onboarding processs.",
  ]
  for line in random.sample(lines, random.randint(3, len(lines) - 1)):
    yield line + " "

<example>

<example>
# This is an example of an advanced chat app.
#
# Features
#
# - Header with title
# - Sidebar
# - Start new chat
# - Focus input
# - Dark mode
# - Rate responses
# - Regenerate responses
# - Examples
import random
import time
from dataclasses import dataclass
from typing import Literal

import mesop as me

Role = Literal["user", "bot"]
# Render me.markdown if markdown
# Render me.image if image
MessageType = Literal["markdown", "image"]


EXAMPLE_USER_QUERIES = (
  "Create a basic chat UI.",
  "Create a chat UI that renders content side by side from multiple LLMs.",
  "Create an advanced chat UI with a header and sidebar.",
)


@dataclass(kw_only=True)
class ChatMessage:
  """Chat message metadata."""

  role: Role = "user"
  content: str = ""
  edited: bool = False
  # 1 is positive
  # -1 is negative
  # 0 is no rating
  rating: int = 0
  message_type: MessageType = "markdown"


@me.stateclass
class State:
  input: str
  output: list[ChatMessage]
  in_progress: bool
  sidebar_expanded: bool = False


@me.page()
def advanced_chat():
  is_mobile = me.viewport_size().width < 640
  state = me.state(State)
  # This is the grid that manages the layout.
  with me.box(
    style=me.Style(
      display="grid",
      # First column is for the sidebar
      # We use 1fr when the sidebar is not expanded and 7fr when it is expanded. This
      # is because the sidebar takes up more space.
      grid_template_columns="7fr 50fr"
      if state.sidebar_expanded and not is_mobile
      else "1fr 50fr",
      # First row is for the header which is why we use 1fr.
      grid_template_rows="1fr 50fr",
      height="100%",
    )
  ):
    # This block is the code for the sidebar
    with me.box(
      style=me.Style(
        grid_row="1 / -1",
        background=me.theme_var("surface-container"),
        border=me.Border.symmetric(
          horizontal=me.BorderSide(
            width=1, style="solid", color=me.theme_var("outline-variant")
          )
        ),
        height="100%",
      )
    ):
      # This block is code for the sidebar menu item.
      # It needs click event handlers to add interaction.
      with me.box(
        # Event handler to expand/collapse the sidebar.
        on_click=on_click_menu_icon,
        style=me.Style(
          cursor="pointer",
          padding=me.Padding.all(15),
        ),
      ):
        me.icon("menu")

      # This block is code for the sidebar menu item.
      # It needs click event handlers to add interaction.
      with me.box(
        on_click=on_click_new_chat,
        style=me.Style(
          cursor="pointer",
          padding=me.Padding.all(15),
        ),
      ):
        if state.sidebar_expanded and not is_mobile:
          with me.box(
            style=me.Style(
              display="flex",
              align_items="center",
              gap=5,
            )
          ):
            me.icon("add")
            me.text("New chat")
        else:
          with me.tooltip(message="New chat"):
            me.icon("add")

      # This block is code for the sidebar menu item.
      # It needs click event handlers to add interaction.
      with me.box(
        on_click=on_click_theme_brightness,
        style=me.Style(
          cursor="pointer",
          padding=me.Padding.all(15),
        ),
      ):
        if state.sidebar_expanded and not is_mobile:
          with me.box(
            style=me.Style(
              display="flex",
              align_items="center",
              gap=5,
            )
          ):
            me.icon(
              "light_mode" if me.theme_brightness() == "dark" else "dark_mode",
            )
            me.text(
              "Light mode" if me.theme_brightness() == "dark" else "Dark mode"
            )
        else:
          with me.tooltip(
            message="Light mode"
            if me.theme_brightness() == "dark"
            else "Dark mode"
          ):
            me.icon(
              "light_mode" if me.theme_brightness() == "dark" else "dark_mode"
            )

    with me.box(
      style=me.Style(
        background=me.theme_var("surface-container"),
        padding=me.Padding.all(10),
        border=me.Border(
          bottom=me.BorderSide(
            width=1, style="solid", color=me.theme_var("outline-variant")
          )
        ),
      )
    ):
      if is_mobile:
        default_flex_style = me.Style(
          align_items="center",
          display="flex",
          gap=5,
          justify_content="space-between",
        )
      else:
        default_flex_style = me.Style(
          align_items="center",
          display="flex",
          gap=5,
          justify_content="space-between",
        )

      with me.box(style=default_flex_style):
        with me.box(style=me.Style(display="flex", gap=5)):
          me.text(
            "Advanced Chat UI",
            type="headline-6",
            style=me.Style(margin=me.Margin(bottom=0)),
          )

        # Only show the "Made with Mesop" message on non-mobile screens.
        if not is_mobile:
          with me.box(style=me.Style(display="flex", gap=5)):
            me.text(
              "Made with ",
              style=me.Style(
                color=me.theme_var("on-surface-variant"),
                font_weight="bold",
                font_size=13,
              ),
            )
            me.link(
              text="Mesop",
              url="https://google.github.io/mesop/",
              open_in_new_tab=True,
              style=me.Style(
                color=me.theme_var("primary"),
                text_decoration="none",
                font_weight="bold",
                font_size=13,
              ),
            )

    # This block is for the main content to be added.
    with me.box(style=me.Style(overflow_y="hidden")):
      with me.box(
        style=me.Style(
          color=me.theme_var("on-surface"),
          background=me.theme_var("surface-container-lowest"),
          display="flex",
          flex_direction="column",
          padding=me.Padding.all(15),
          height="100%",
        )
      ):
        # If there are no messages yet, show some example queries for the user to get
        # started with.
        if not state.output:
          with me.box(
            style=me.Style(
              overflow_y="scroll",
              flex_grow=1,
              color=me.theme_var("on-surface-variant"),
            )
          ):
            with me.box(style=me.Style(margin=me.Margin(top=25), font_size=20)):
              me.text("Get started with an example below")
            with me.box(
              style=me.Style(display="flex", gap=20, margin=me.Margin(top=25))
            ):
              for index, query in enumerate(EXAMPLE_USER_QUERIES):
                with me.box(
                  key=f"query-{index}",
                  on_click=on_click_example_user_query,
                  style=me.Style(
                    background=me.theme_var("surface-container-highest"),
                    border_radius=15,
                    padding=me.Padding.all(20),
                    cursor="pointer",
                  ),
                ):
                  me.text(query)

        else:
          # This contains the chat messages that have been recorded. This takes 50fr.
          # This section can be replaced with other types of chat messages.

          # We set overflow to scroll so that the chat input will be fixed at the bottom.
          with me.box(style=me.Style(overflow_y="scroll", flex_grow=1)):
            for index, msg in enumerate(state.output):
              # User chat message
              if msg.role == "user":
                with me.box(
                  style=me.Style(
                    display="flex",
                    justify_content="end",
                    gap=15,
                    margin=me.Margin.all(20),
                  )
                ):
                  with me.box(
                    style=me.Style(
                      border_radius=10,
                      background=me.theme_var("surface-container"),
                      color=me.theme_var("on-surface-variant"),
                      padding=me.Padding.symmetric(vertical=0, horizontal=10),
                      width="66%",
                    )
                  ):
                    # User query
                    me.markdown(msg.content)
              else:
                # Bot chat message
                with me.box(
                  style=me.Style(
                    display="flex", gap=15, margin=me.Margin.all(20)
                  )
                ):
                  # Bot avatar/icon box
                  me.text(
                    "M",
                    style=me.Style(
                      background=me.theme_var("primary"),
                      border_radius="50%",
                      color=me.theme_var("on-primary"),
                      font_size=20,
                      height=40,
                      width="40px",
                      text_align="center",
                      line_height="1",
                      padding=me.Padding(top=10),
                      margin=me.Margin(top=16),
                    ),
                  )
                  # Bot message response
                  with me.box():
                    me.markdown(
                      msg.content,
                      style=me.Style(color=me.theme_var("on-surface")),
                    )

                    rated_style = me.Style(
                      background=me.theme_var("surface-container-low"),
                      color=me.theme_var("on-surface-variant"),
                    )
                    with me.tooltip(message="Good response", position="above"):
                      with me.content_button(
                        type="icon",
                        key=f"thumb_up-{index}",
                        on_click=on_click_thumb_up,
                        style=rated_style if msg.rating == 1 else None,
                      ):
                        me.icon("thumb_up")

                    with me.tooltip(message="Bad response", position="above"):
                      with me.content_button(
                        type="icon",
                        key=f"thumb_down-{index}",
                        on_click=on_click_thumb_down,
                        style=rated_style if msg.rating == -1 else None,
                      ):
                        me.icon("thumb_down")

                    with me.tooltip(
                      message="Regenerate answer", position="above"
                    ):
                      with me.content_button(
                        type="icon",
                        key=f"restart-{index}",
                        on_click=on_click_regenerate,
                      ):
                        me.icon("restart_alt")

        # This is for the basic chat input. This is the second row at 1fr.
        # This section can be replaced with other types of chat inputs.
        with me.box(
          style=me.Style(
            border_radius=16,
            padding=me.Padding.all(8),
            background=me.theme_var("surface-container-low"),
            display="flex",
          )
        ):
          with me.box(
            style=me.Style(
              flex_grow=1,
            )
          ):
            me.native_textarea(
              key="chat_input",
              value=state.input,
              on_blur=on_chat_input,
              autosize=True,
              min_rows=4,
              placeholder="Subtle chat input",
              style=me.Style(
                color=me.theme_var("on-surface-variant"),
                padding=me.Padding(top=16, left=16),
                background=me.theme_var("surface-container-low"),
                outline="none",
                width="100%",
                overflow_y="auto",
                border=me.Border.all(
                  me.BorderSide(style="none"),
                ),
              ),
            )
          with me.content_button(
            type="icon",
            on_click=on_click_submit_chat_msg,
            # If we're processing a message prevent new queries from being sent
            disabled=state.in_progress,
          ):
            me.icon("send")


def on_click_example_user_query(e: me.ClickEvent):
  """Populates the user input with the example query"""
  state = me.state(State)
  # Get the example index from the key
  _, example_index = e.key.split("-")
  state.input = EXAMPLE_USER_QUERIES[int(example_index)]


def on_click_thumb_up(e: me.ClickEvent):
  """Gives the message a positive rating"""
  state = me.state(State)
  # Get the message index from the key
  _, msg_index = e.key.split("-")
  msg_index = int(msg_index)
  # Give a positive rating
  state.output[msg_index].rating = 1


def on_click_thumb_down(e: me.ClickEvent):
  """Gives the message a negative rating"""
  state = me.state(State)
  # Get the message index from the key
  _, msg_index = e.key.split("-")
  msg_index = int(msg_index)
  # Give a negative rating
  state.output[msg_index].rating = -1


def on_click_new_chat(e: me.ClickEvent):
  """Resets messages."""
  state = me.state(State)
  state.output = []
  me.focus_component(key="chat_input")


def on_click_theme_brightness(e: me.ClickEvent):
  """Toggles dark mode."""
  if me.theme_brightness() == "light":
    me.set_theme_mode("dark")
  else:
    me.set_theme_mode("light")


def on_click_menu_icon(e: me.ClickEvent):
  """Expands and collapses sidebar menu."""
  state = me.state(State)
  state.sidebar_expanded = not state.sidebar_expanded


def on_chat_input(e: me.InputBlurEvent):
  """Capture chat text input on blur."""
  state = me.state(State)
  state.input = e.value


def on_click_regenerate(e: me.ClickEvent):
  """Regenerates response from an existing message"""
  state = me.state(State)
  # Get message index from key
  _, msg_index = e.key.split("-")
  msg_index = int(msg_index)

  # Get the user message which is the previous message
  user_message = state.output[msg_index - 1]
  # Get bot message to be regenerated
  assistant_message = state.output[msg_index]
  assistant_message.content = ""
  state.in_progress = True
  yield

  start_time = time.time()
  # Send in the old user input and chat history to get the bot response.
  # We make sure to only pass in the chat history up to this message.
  output_message = respond_to_chat(
    user_message.content, state.output[:msg_index]
  )
  for content in output_message:
    assistant_message.content += content
    # TODO: 0.25 is an abitrary choice. In the future, consider making this adjustable.
    if (time.time() - start_time) >= 0.25:
      start_time = time.time()
      yield

  state.in_progress = False
  me.focus_component(key="chat_input")
  yield


def on_click_submit_chat_msg(e: me.ClickEvent):
  """Handles submitting a chat message."""
  state = me.state(State)
  if state.in_progress or not state.input:
    return
  input = state.input
  # Clear the text input.
  state.input = ""
  yield

  output = state.output
  if output is None:
    output = []
  output.append(ChatMessage(role="user", content=input))
  state.in_progress = True
  yield

  start_time = time.time()
  # Send user input and chat history to get the bot response.
  output_message = respond_to_chat(input, state.output)
  assistant_message = ChatMessage(role="bot")
  output.append(assistant_message)
  state.output = output
  for content in output_message:
    assistant_message.content += content
    # TODO: 0.25 is an abitrary choice. In the future, consider making this adjustable.
    if (time.time() - start_time) >= 0.25:
      start_time = time.time()
      yield

  state.in_progress = False
  me.focus_component(key="chat_input")
  yield


def respond_to_chat(input: str, history: list[ChatMessage]):
  """Displays random canned text.

  Edit this function to process messages with a real chatbot/LLM.
  """
  lines = [
    "Mesop is a Python-based UI framework designed to simplify web UI development for engineers without frontend experience.",
    "It leverages the power of the Angular web framework and Angular Material components, allowing rapid construction of web demos and internal tools.",
    "With Mesop, developers can enjoy a fast build-edit-refresh loop thanks to its hot reload feature, making UI tweaks and component integration seamless.",
    "Deployment is straightforward, utilizing standard HTTP technologies.",
    "Mesop's component library aims for comprehensive Angular Material component coverage, enhancing UI flexibility and composability.",
    "It supports custom components for specific use cases, ensuring developers can extend its capabilities to fit their unique requirements.",
    "Mesop's roadmap includes expanding its component library and simplifying the onboarding processs.",
  ]

  for line in random.sample(lines, random.randint(3, len(lines) - 1)):
    yield line + " "

<example>