Trying to make Gemini prompt better.

Reviewed-on: #4

.gitignore

@@ -1,13 +1,8 @@
 .DS_Store
 extracted_texts/**
-!extracted_texts/.gitkeep
 intermediates/**
-!intermediates/.gitkeep
 cover_briefs/**
-!cover_briefs/.gitkeep
 for_gemini/**
-!for_gemini/.gitkeep
 raw_ebooks/**
-!raw_ebooks/.gitkeep
 config.json
 config.json.lock

ReadMe.md

@@ -1,40 +1,76 @@
 # llm-covers
+Makes placeholder cover briefs for ebooks.
+
 A simple tool for using local LLMs to generate cover briefs for ebooks.
 
 ## Requirements
 - A Mac mini M4 base model (original version) or better M-series computer
 - Ollama and `gemma4:12b-mlx`
 - LuaJIT
+- calibre
 
 ## Usage
-1. Use a tool like [audiobook-creator](https://github.com/prakharsr/audiobook-creator) to extract the text of an audiobook.
-2. Place it in `extracted_texts/TITLE by AUTHOR.txt`. (The format of this doesn't matter except that the file name sans extension will be used in the output.)
-3. Run `make_cover_briefs.lua`.
-4. Cover briefs will be placed in `cover_briefs`.
-5. A prompt ready to paste directly into Gemini will be in `for_gemini`. An extra border is prompted for to make cropping easy to remove the Gemini watermark. (There are other small changes to increase likelihood of Gemini following the prompt correctly and making a good output.)
+1. Create `config.json` if necessary (see format below).
+2. Run `make_cover_briefs.lua` once to create necessary directories.
+3. Put ebooks in `raw_ebooks`.
+4. Run `make_cover_briefs.lua`
+
+Cover briefs will be placed in `cover_briefs`. A prompt ready to paste directly
+into Gemini will be in `for_gemini`.
+
+The local model sometimes completely forgets critical details of characters, so
+it's important you have some familiarity with the work before running the
+generator to check accuracy.
+
+### Config file format
+```json
+{
+  "llm_covers": {
+    "calibre_location": "/Applications/calibre.app",
+    "default_model": "gemma4:12b-mlx",
+    "maximum_bytes": 40000
+  }
+}
+```
+
+The above are the default settings. If you need something different, you only
+need to specify the changes. (There is a `config.json.example` file equivalent
+to the above.)
 
 ### Gemini Issues
-None of this works unless you **disable Gemini's personalization/memory**, because it pollutes context
-extremely badly and will randomly add elements and rejections from different conversations everywhere.
+None of this works unless you **disable Gemini's personalization/memory**,
+because it pollutes context extremely badly and will randomly add elements and
+rejections from different conversations everywhere.
 
-If Gemini rejects the prompt, adding <code id="d2651e">Remove any elements that may go against guidelines before generating the image.</code>
+If you are able to use Gemini Flash or Flash-Lite, it works far better than Pro.
+Pro tends to invent additional details, refuse to respond, fail to respond, or
+make modifications you didn't ask for. I genuinely cannot understand how it is
+*so much worse* at this.
+
+Gemini is really bad about adding hardcover seams. Despite being instructed not
+to, it shows up often. More strong prompting breaks other requested
+features, so the best way to deal with it is to request its removal after the
+initial image is generated.
+
+If Gemini rejects the prompt, adding
+<code id="d2651e">Remove any elements that may go against guidelines before generating the image.</code>
 <button onclick="navigator.clipboard.writeText(d2651e.textContent)">⧉</button>
-to the opening paragraph can fix that issue.
-- This suddenly got a lot less effective. I recommend instead telling it to rewrite the prompt and then
-  in a separate conversation, use that instead. I also recommend one retry before modifying it.
-
-Gemini is really bad about adding hardcover seams. Despite being instructed not to, it shows up sometimes.
-More strong prompting breaks other requested features, so the best way to deal with it is to request its
-removal after the initial image is generated.
-
-The local model sometimes completely forgets critical details of characters,
-so it's important you have some familiarity with the work before running the generator
-to check accuracy.
+to the opening paragraph can *sometimes* fix that issue.
+- Telling it to rewrite the prompt and then using *that* in a separate
+  conversation tends to work better.
+- I typically just re-send it repeatedly, as it's easier and eventually works
+  most of the time.
 
 ## Tasks
 - [ ] Add timestamps to when a prompt is sent.
-- [ ] Specify ETA when sending a prompt (1.5-8 minutes depending on length). (Show as end time as well as relative time.)
-- [ ] option to delete input files or intermediate files at end of each operation step
-- [ ] make script resumable instead of having to restart per book
-- [ ] instead of placeholder directories, `mkdir -p` should be used to only make them when necessary
-- [ ] dry run to estimate total time before running full script, print starting ETA
+- [ ] Specify ETA when sending a prompt (use numbers from current estimator depending on length). (Show as end time as well as relative time.)
+- [ ] option to delete input files or intermediate files at end of each major operation segment (or after its finisher..)
+- [ ] Allow specifying a filter on what to process
+- [ ] Allow changing the maximum bytes per prompt dynamically (run smaller while I'm doing other things, run full while I'm asleep)
+- [ ] `argparse` + ability to
+  - [ ] only convert ebooks or
+  - [ ] only generate cover briefs or
+  - [ ] only generate single pass cover briefs or
+  - [ ] list how many are left only
+- [x] I have an item with over 300 parts in it. Another level of compression needs to be added!
+- [ ] Change Gemini prompt because it is *obsessed* with putting colons EVERYWHERE.

config.json.example

@@ -1,5 +1,7 @@
 {
   "llm_covers": {
-    "calibre_location": "/Applications/calibre.app"
+    "calibre_location": "/Applications/calibre.app",
+    "default_model": "gemma4:12b-mlx",
+    "maximum_bytes": 40000
   }
 }

convert_epubs_to_txt.lua

@@ -1,22 +0,0 @@
-#!/usr/bin/env luajit
-
-package.path = (arg[0]:match("@?(.*/)") or arg[0]:match("@?(.*\\)")) .. "lib" .. package.config:sub(1, 1) .. "?.lua;" .. package.path
-local utility = require "utility"
-
-local calibre_location = "/Applications/calibre.app"
-local config = utility.get_config("read-only")
-if config and config.llm_covers and config.llm_covers.calibre_location then
-  calibre_location = config.llm_covers.calibre_location
-end
-
-utility.ls("raw_ebooks", function(file_name)
-  local _, name, extension = utility.split_path_components(file_name)
-  if extension then
-    name = name:sub(1, -(#extension + 2))
-  end
-
-  local output_name = "extracted_texts/" .. name .. ".txt"
-  if utility.path_exists(output_name) then return end
-
-  os.execute(calibre_location .. "/Contents/MacOS/ebook-convert " .. ("raw_ebooks/" .. file_name):enquote() .. " " .. output_name:enquote())
-end)

count_characters.lua

@@ -3,7 +3,9 @@
 package.path = (arg[0]:match("@?(.*/)") or arg[0]:match("@?(.*\\)")) .. "lib" .. package.config:sub(1, 1) .. "?.lua;" .. package.path
 local utility = require "utility"
 
-local maximum_bytes = 40000
+local config = utility.get_config("read-only")
+if not config.llm_covers then config.llm_covers = {} end
+if not config.llm_covers.maximum_bytes then config.llm_covers.maximum_bytes = 40000 end
 
 local read_all = function(file_name)
   return utility.open(file_name, "r", function(file)
@@ -25,7 +27,7 @@ for _, path in ipairs{ ".", "extracted_texts", } do
     local path, name, extension = utility.split_path_components(file_name)
     local text = read_all(file_name)
 
-    print(math.floor(#text/maximum_bytes + 1), math.floor(#text/1000) .. "k", name)
+    print(math.floor(#text/config.llm_covers.maximum_bytes + 1), math.floor(#text/1000) .. "k", name)
   end)
   print("Press enter.")
   io.read("*line")

lib/prompts.lua

@@ -0,0 +1,70 @@
+local prompts = {}
+
+prompts.section_summarization = [[You are extracting information for a later cover design process.
+
+This is only one section of a larger story.
+
+Do NOT attempt to design a cover.
+Do NOT decide what should appear on the cover.
+Do NOT write a summary.
+
+Extract only information that may be useful when creating a cover after all story sections have been analyzed.
+
+Return:
+
+GENRE:
+- up to 5 items
+
+SETTING:
+- locations
+- environments
+- time period
+
+CHARACTERS:
+- names
+- physical descriptions
+- distinctive visual traits
+
+CREATURES:
+- notable creatures
+
+OBJECTS:
+- important recurring items
+
+VISUAL MOTIFS:
+- recurring imagery
+- symbols
+- repeated visual elements
+
+THEMES:
+- major themes
+
+MOOD:
+- emotional tone
+
+COLORS:
+- colors strongly associated with scenes or imagery
+
+MEMORABLE VISUAL SCENES:
+- 3-10 visually striking moments
+
+CONFIDENCE:
+- how central each item appears to be
+
+]]
+
+prompts.combine_summaries = [[Take the common portions from the following text and produce a single simplified list of information:
+
+]]
+
+prompts.cover_brief = [[Generate a cover brief from the following:
+
+]]
+
+prompts.for_gemini = [[
+
+Generate an ebook cover using the following cover brief. It should be a flat graphic design file, with no artifacts of a physical object. The aspect ratio of an ebook is tall, not wide. The title and author should only appear once on the cover. It must be sutiable for printing. Do not include the word "by" on the cover. An underscore in the title should be replaced with a colon, but not hyphens or as a separator between the title and author. The author is separated from the title by the last hyphen on the line showing the title and author.
+
+]]
+
+return prompts

lib/timing.lua

@@ -0,0 +1,38 @@
+local timing = {}
+local entries = {}
+
+function timing.seconds_to_minutes(seconds)   -- floored to tenths
+  return math.floor( seconds / 60 * 10 ) / 10
+end
+
+function timing.start()
+  entries[#entries + 1] = { start_time = os.time() }
+end
+
+function timing.stop()
+  local entry = entries[#entries]
+  entry.stop_time = os.time()
+  entry.delta = entry.stop_time - entry.start_time
+
+  return timing.seconds_to_minutes(entry.delta)
+end
+
+function timing.print_report()
+  if #entries == 0 then return end
+
+  local minimum, maximum, sum = math.huge, -math.huge, 0
+  for _, data in pairs(entries) do
+    local delta = data.delta
+    if delta > maximum then maximum = delta end
+    if delta < minimum then minimum = delta end
+    sum = sum + delta
+  end
+
+  print("Total: " .. timing.seconds_to_minutes(sum) .. " minutes.")
+  print("Averge: " .. timing.seconds_to_minutes(sum / #entries)
+    .. " minutes. Fastest: " .. timing.seconds_to_minutes(minimum)
+    .. " minutes. Slowest: " .. timing.seconds_to_minutes(maximum)
+    .. " minutes.")
+end
+
+return timing

lib/utility.lua

@@ -32,7 +32,7 @@ else
   }
 end
 
-utility.version = "1.4.0"
+utility.version = "1.5.2"
 -- WARNING: This will return "./" if the original script is called locally instead of with an absolute path!
 if arg[0] ~= nil then
   utility.path = (arg[0]:match("@?(.*/)") or arg[0]:match("@?(.*\\)")) -- inspired by discussion in https://stackoverflow.com/q/6380820
@@ -124,14 +124,6 @@ standard_library_addition(string, "enquote", function(s)
   return "\"" .. s:gsub("\"", "\\\"") .. "\""
 end)
 
-standard_library_addition(string, "split", function(s, delimiter)
-  local result = {}
-  for item in s:gsplit(delimiter) do
-    result[#result + 1] = item
-  end
-  return result
-end)
-
 standard_library_addition(string, "gsplit", function(s, delimiter)
   local function escape_special_characters(s)
     local special_characters = "[()%%.[^$%]*+%-?]"
@@ -144,6 +136,14 @@ standard_library_addition(string, "gsplit", function(s, delimiter)
   return s:gmatch("(.-)" .. escape_special_characters(delimiter))
 end)
 
+standard_library_addition(string, "split", function(s, delimiter)
+  local result = {}
+  for item in s:gsplit(delimiter) do
+    result[#result + 1] = item
+  end
+  return result
+end)
+
 
 
 -- modified from my fork of lume
@@ -301,7 +301,7 @@ utility.release_lock = function(file_path, lock_uuid)
   local lock_file_path = file_path .. ".lock"
   if lock_uuid then
     utility.open(lock_file_path, "r", function(file)
-      if not file:read("*all") == lock_uuid then
+      if not (file:read("*all") == lock_uuid) then
         error("\n\n Lock UUID changed while lock was obtained. Data loss may have occurred. \n\n")
       end
     end)
@@ -348,12 +348,47 @@ utility.save_config = function()
   end
 end
 
+local data_file_locations = {}
+utility.load_data = function(file_path)
+  local data = utility.open(file_path, "r", function(data_file)
+    local json = utility.require("dkjson")
+    return json.decode(data_file:read("*all"))
+  end)
+  data_file_locations[data] = file_path
+  return data
+end
+
+utility.save_data = function(data, file_path)
+  local keys, loop = {}
+  loop = function(tab)
+    if type(tab) == "table" then
+      for k,v in pairs(tab) do
+        if not (type(k) == "number") then
+          keys[k] = true
+        end
+        loop(v)
+      end
+    end
+  end
+  loop(data)
+  local order = {}
+  for k in pairs(keys) do order[#order + 1] = k end
+  table.sort(order)
+
+  file_path = file_path or data_file_locations[data]
+  assert(file_path, "The object must have been loaded by utility.load_data or you must pass a path as the second argument.")
+  utility.open(file_path, "w", function(data_file)
+    local json = utility.require("dkjson")
+    data_file:write(json.encode(data, { indent = true, keyorder = order, }))
+    data_file:write("\n")
+  end)
+end
+
 
 
 utility.deepcopy = function(tab)
-  local _type = type(tab)
   local copy
-  if _type == "table" then
+  if type(tab) == "table" then
     copy = {}
     for key, value in next, tab, nil do
       copy[utility.deepcopy(key)] = utility.deepcopy(value)

make_cover_briefs.lua

@@ -2,87 +2,14 @@
 
 package.path = (arg[0]:match("@?(.*/)") or arg[0]:match("@?(.*\\)")) .. "lib" .. package.config:sub(1, 1) .. "?.lua;" .. package.path
 local utility = require "utility"
+local prompts = require "prompts"
+local timing = require "timing"
 
-local default_model = "gemma4:12b-mlx"
-local maximum_bytes = 40000
-
-local partial_prompt = [[You are extracting information for a later cover design process.
-
-This is only one section of a larger story.
-
-Do NOT attempt to design a cover.
-Do NOT decide what should appear on the cover.
-Do NOT write a summary.
-
-Extract only information that may be useful when creating a cover after all story sections have been analyzed.
-
-Return:
-
-GENRE:
-- up to 5 items
-
-SETTING:
-- locations
-- environments
-- time period
-
-CHARACTERS:
-- names
-- physical descriptions
-- distinctive visual traits
-
-CREATURES:
-- notable creatures
-
-OBJECTS:
-- important recurring items
-
-VISUAL MOTIFS:
-- recurring imagery
-- symbols
-- repeated visual elements
-
-THEMES:
-- major themes
-
-MOOD:
-- emotional tone
-
-COLORS:
-- colors strongly associated with scenes or imagery
-
-MEMORABLE VISUAL SCENES:
-- 3-10 visually striking moments
-
-CONFIDENCE:
-- how central each item appears to be
-
-]]
-
-local squish_partials_prompt = [[Take the common portions from the following text and produce a single simplified list of information:
-
-]]
-
-local cover_brief_prompt = [[Generate a cover brief from the following:
-
-]]
-
-local segmented_cover_brief_prompt = [[Generate a single cover brief.
-
-Prefer elements that:
-- appear repeatedly across chunks
-- have highest confidence
-- best represent the entire story
-
-Avoid minor plot events.
-
-]]
-
-local gemini_prompt = [[
-
-Generate an ebook cover inset within an empty white border 10% larger than the cover using the following cover brief. It should be a flat graphic design file, with no artifacts of a physical object. The aspect ratio of an ebook is tall, not wide. The white border is very important, and should take up 10% of the area of the image. The title and author should only appear once on the cover. It must be sutiable for printing. Do not include the word "by" when adding the author's name to the cover.
-
-]]
+local config = utility.get_config("read-only")
+if not config.llm_covers then config.llm_covers = {} end
+if not config.llm_covers.calibre_location then config.llm_covers.calibre_location = "/Applications/calibre.app" end
+if not config.llm_covers.default_model then config.llm_covers.default_model = "gemma4:12b-mlx" end
+if not config.llm_covers.maximum_bytes then config.llm_covers.maximum_bytes = 40000 end
 
 local read_all = function(file_name)
   return utility.open(file_name, "r", function(file)
@@ -96,19 +23,6 @@ local write_all = function(file_name, text)
   end)
 end
 
-local timings = {}
-local timing_report = function()
-  local minimum, maximum, sum = math.huge, 0, 0
-  for _, delta in ipairs(timings) do
-    if delta > maximum then maximum = delta end
-    if delta < minimum then minimum = delta end
-    sum = sum + delta
-  end
-  print("")
-  print("Prompts took a total of " .. sum .. " minutes.")
-  print("Average: " .. math.floor(sum / #timings) .. " minutes. Fastest: " .. minimum .. " minutes. Slowest: " .. maximum .. " minutes.")
-end
-
 local strip_reasoning = function(text, reasoning_lines)
   if not reasoning_lines then reasoning_lines = {} end
   local tab = text:split("\n")
@@ -136,22 +50,29 @@ local send_prompt = function(text, model)
     file:write(text)
   end)
 
-  local start_time = os.time()
+  timing.start()
   -- word wrap breaks the raw output badly, so I need to implement my own for terminal output somehow
-  local output = utility.capture_safe("cat " .. tmp_file_name:enquote() .. " | ollama run " .. (model or default_model) .. " --nowordwrap")
-  os.execute("ollama stop " .. (model or default_model)) -- NOTE this makes things slower, but more stable
-  local delta = math.floor( (os.time() - start_time) / 60 * 10 ) / 10
+  local output = utility.capture_safe("cat " .. tmp_file_name:enquote() .. " | ollama run " .. (model or config.llm_covers.default_model) .. " --nowordwrap")
+  os.execute("ollama stop " .. (model or config.llm_covers.default_model)) -- NOTE this makes things slower, but more stable
+  local delta = timing.stop()
+
   print("Took " .. delta .. " minutes.")
-  timings[#timings + 1] = delta
   os.execute("rm " .. tmp_file_name)
   if not output then error("ollama failed to generate output") end
+
   output = output:sub(1, -2) -- strip extra newline from utility.capture_safe
-
   output = strip_reasoning(output)
-
   return output
 end
 
+local make_directories = function()
+  os.execute("mkdir -p raw_ebooks" .. utility.commands.silence_output)
+  os.execute("mkdir -p extracted_texts" .. utility.commands.silence_output)
+  os.execute("mkdir -p intermediates" .. utility.commands.silence_output)
+  os.execute("mkdir -p cover_briefs" .. utility.commands.silence_output)
+  os.execute("mkdir -p for_gemini" .. utility.commands.silence_output)
+end
+
 local tree
 tree = function(path, fn)
   utility.list(path or ".", function(path_name)
@@ -170,54 +91,262 @@ tree = function(path, fn)
   end)
 end
 
-tree("extracted_texts", function(file_name)
-  local path, name, extension = utility.split_path_components(file_name)
-  if utility.path_exists("cover_briefs/" .. name) then return end
+local find_ebook_files = function(books)
+  if not books then books = {} end
 
-  local text = read_all(file_name)
-  local result
-
-  print(name)
-  local outputs = {}
-  if #text > maximum_bytes then
-    -- TODO check if this would work just as well starting from 1 instead..
-    for i = 0, #text/maximum_bytes do
-      print("Processing section " .. (i + 1) .. " of " .. math.floor(#text/maximum_bytes + 1))
-      local piece = text:sub(i * maximum_bytes, (i + 1) * maximum_bytes - 1)
-      result = send_prompt(partial_prompt .. piece)
-      outputs[#outputs + 1] = result
-      print(#result .. " characters added to intermediate context.")
+  tree("raw_ebooks", function(file_name)
+    local _, name, extension = utility.split_path_components(file_name)
+    if extension then
+      name = name:sub(1, -(#extension + 2))
     end
 
-    text = table.concat(outputs, "\n\n")
-    write_all("intermediates/" .. name, text)
+    if not books[name] then
+      books[name] = {}
+    end
+    books[name].ebook_file = file_name
+  end)
+
+  return books
+end
+
+local find_extracted_texts = function(books)
+  if not books then books = {} end
+
+  tree("extracted_texts", function(file_name)
+    local _, name, extension = utility.split_path_components(file_name)
+    if extension then
+      name = name:sub(1, -(#extension + 2))
     end
 
-  -- handle too much context (works with up to 100 slices)
-  if #outputs > 10 then
-    local context_slices = {}
-    while #outputs > 2 do
-      local output_slices = {}
+    if not books[name] then
+      books[name] = {}
+    end
+    books[name].extracted_file = file_name
+    books[name].extracted_file_size = utility.file_size(file_name)
+  end)
+
+  return books
+end
+
+local find_cover_briefs = function(books)
+  if not books then books = {} end
+
+  tree("cover_briefs", function(file_name)
+    local _, name, extension = utility.split_path_components(file_name)
+    if extension then
+      name = name:sub(1, -(#extension + 2))
+    end
+
+    if not books[name] then
+      books[name] = {}
+    end
+    books[name].cover_brief_file = file_name
+  end)
+
+  return books
+end
+
+local get_books = function()
+  local books = {}
+  find_ebook_files(books)
+  find_extracted_texts(books)
+  find_cover_briefs(books)
+  return books
+end
+
+local convert_ebooks = function(books)
+  for name, data in pairs(books) do
+    local function loop()
+      if data.extracted_file then return end
+      if not data.ebook_file then return end
+
+      local extracted_file = "extracted_texts/" .. name .. ".txt"
+      os.execute(config.llm_covers.calibre_location .. "/Contents/MacOS/ebook-convert "
+        .. data.ebook_file:enquote() .. " " .. extracted_file:enquote())
+
+      if utility.path_exists(extracted_file) then
+        data.extracted_file = extracted_file
+        data.extracted_file_size = utility.file_size(extracted_file)
+      end
+    end
+    loop()
+  end
+end
+
+-- TODO deal with the fact that this function is a clone with only a couple line changes
+local compress_it_again = function(name, data, sections)
+  local condensed_sections = {}
+
+  while #sections > 2 do -- this intentionally can skip the end of a book?
+    local sections_slice = {}
     for i = 1, 10 do
-        if #outputs >= 1 then
-          output_slices[#output_slices + 1] = table.remove(outputs, 1)
+      if #sections >= 1 then
+        sections_slice[#sections_slice + 1] = table.remove(sections, 1)
       end
     end
 
-      print("Squishing context. " .. #outputs .. " samples remaining.")
-      result = send_prompt(squish_partials_prompt .. table.concat(output_slices, "\n\n"))
-      context_slices[#context_slices + 1] = result
-      print(#result .. " characters added to final context.")
+    local intermediate_condensation_file = "intermediates/" .. name .. "-" .. (#condensed_sections + 1) .. "-super-condensed.txt"
+    if utility.path_exists(intermediate_condensation_file) then
+      condensed_sections[#condensed_sections + 1] = read_all(intermediate_condensation_file)
+      print("Loaded condensed summary segment. " .. #sections .. " sections remaining.")
+    else
+      print("Condensing summary. " .. #sections .. " sections remaining.")
+      local text = send_prompt(prompts.combine_summaries .. table.concat(sections_slice, "\n\n"))
+      condensed_sections[#condensed_sections + 1] = text
+      print(#text .. " characters added to final context.")
+      write_all(intermediate_condensation_file, text)
+    end
   end
 
-    text = table.concat(context_slices, "\n\n")
-    write_all("intermediates/" .. name:sub(1, -5) .. " CONDENSED.txt", text)
+  text = table.concat(condensed_sections, "\n\n")
+  local condensed_intermediate_file = "intermediates/" .. name .. " SUPER CONDENSED.txt"
+  write_all(condensed_intermediate_file, text)
+  data.condensed_intermediate_file = condensed_intermediate_file
+
+  -- if deleted any sooner, could break resuming
+  for i = 1, #condensed_sections do
+    local intermediate_condensation_file = "intermediates/" .. name .. "-" .. i .. "-super-condensed.txt"
+    os.execute("rm " .. intermediate_condensation_file:enquote())
+  end
+
+  return text
+end
+
+local condense_summary = function(name, data, sections)
+  local condensed_sections = {}
+
+  while #sections > 2 do -- this intentionally can skip the end of a book?
+    local sections_slice = {}
+    for i = 1, 10 do
+      if #sections >= 1 then
+        sections_slice[#sections_slice + 1] = table.remove(sections, 1)
+      end
+    end
+
+    local intermediate_condensation_file = "intermediates/" .. name .. "-" .. (#condensed_sections + 1) .. "-condensed.txt"
+    if utility.path_exists(intermediate_condensation_file) then
+      condensed_sections[#condensed_sections + 1] = read_all(intermediate_condensation_file)
+      print("Loaded condensed summary segment. " .. #sections .. " sections remaining.")
+    else
+      print("Condensing summary. " .. #sections .. " sections remaining.")
+      local text = send_prompt(prompts.combine_summaries .. table.concat(sections_slice, "\n\n"))
+      condensed_sections[#condensed_sections + 1] = text
+      print(#text .. " characters added to final context.")
+      write_all(intermediate_condensation_file, text)
+    end
+  end
+
+  text = table.concat(condensed_sections, "\n\n")
+  local condensed_intermediate_file = "intermediates/" .. name .. " CONDENSED.txt"
+  write_all(condensed_intermediate_file, text)
+  data.condensed_intermediate_file = condensed_intermediate_file
+
+  if #condensed_sections > 15 then
+    text = compress_it_again(name, data, condensed_sections)
+  end
+
+  -- if deleted any sooner, could break resuming
+  for i = 1, #condensed_sections do
+    local intermediate_condensation_file = "intermediates/" .. name .. "-" .. i .. "-condensed.txt"
+    os.execute("rm " .. intermediate_condensation_file:enquote())
+  end
+
+  return text
+end
+
+local generate_summary = function(name, data)
+  local text = read_all(data.extracted_file)
+  local sections = {}
+
+  for i = 0, data.extracted_file_size/config.llm_covers.maximum_bytes do
+    local intermediate_section_file = "intermediates/" .. name .. "-" .. i .. ".txt"
+    if utility.path_exists(intermediate_section_file) then
+      sections[#sections + 1] = read_all(intermediate_section_file)
+      print("Loaded section " .. (i + 1) .. ".")
+    else
+      print("Processing section " .. (i + 1) .. " of " .. math.floor(data.extracted_file_size/config.llm_covers.maximum_bytes + 1))
+      local section = text:sub(i * config.llm_covers.maximum_bytes, (i + 1) * config.llm_covers.maximum_bytes - 1)
+      section = send_prompt(prompts.section_summarization .. section)
+      sections[#sections + 1] = section
+      print(#section .. " characters added to intermediate context.")
+      write_all(intermediate_section_file, section)
+    end
+  end
+
+  text = table.concat(sections, "\n\n")
+  local intermediate_file = "intermediates/" .. name .. ".txt"
+  write_all(intermediate_file, text)
+  data.intermediate_file = intermediate_file
+
+  if #sections > 10 then
+    text = condense_summary(name, data, sections)
+  end
+
+  -- if these temporary files are removed before condense_summary is called,
+  --   sections cannot be individually loaded, which breaks condense_summary
+  for i = 0, data.extracted_file_size/config.llm_covers.maximum_bytes do
+    local intermediate_section_file = "intermediates/" .. name .. "-" .. i .. ".txt"
+    os.execute("rm " .. intermediate_section_file:enquote())
+  end
+
+  return text
+end
+
+local generate_cover_briefs = function(books)
+  for name, data in pairs(books) do
+    local function loop()
+      if data.cover_brief_file then return end
+      print(name)
+
+      local text
+      if data.extracted_file_size > config.llm_covers.maximum_bytes then
+        text = generate_summary(name, data)
+      else
+        text = read_all(data.extracted_file)
       end
 
       print("Generating cover brief.")
-  result = send_prompt(cover_brief_prompt .. text)
-  write_all("cover_briefs/" .. name, result)
-  write_all("for_gemini/" .. name, "Title: " .. name:sub(1, -5) .. gemini_prompt .. result)
-end)
+      text = send_prompt(prompts.cover_brief .. text)
 
-timing_report()
+      local cover_brief_file = "cover_briefs/" .. name .. ".txt"
+      write_all(cover_brief_file, text)
+      write_all("for_gemini/" .. name .. ".txt", "Title: " .. name .. prompts.for_gemini .. text)
+      data.cover_brief_file = cover_brief_file
+    end
+    loop()
+  end
+end
+
+local estimate_time_required = function(books)
+  local sum, count = 0, 0
+  for name, data in pairs(books) do
+    local function loop()
+      if data.cover_brief_file then return end
+      if not data.extracted_file then return end
+      sum = sum + 60 * (1.5 + data.extracted_file_size/(config.llm_covers.maximum_bytes/6))
+      count = count + 1
+    end
+    loop()
+  end
+
+  print(count .. " cover briefs to generate. Estimated time: "
+    .. timing.seconds_to_minutes(sum) .. " minutes.")
+end
+
+make_directories()
+
+local books = get_books()
+convert_ebooks(books)
+
+estimate_time_required(books)
+print("")
+
+generate_cover_briefs(books)
+
+print("")
+timing.print_report()
+
+-- utility.print_table(books)
+
+-- ebook_file, extracted_file, extracted_file_size,
+-- intermediate_file, condensed_intermediate_file, cover_brief_file