Claude Code transcript - page 3/6

     1→BEGIN:VCALENDAR
     2→VERSION:2.0
     3→PRODID:-//Pentabarf//Schedule 0.3//EN
     4→CALSCALE:GREGORIAN
     5→METHOD:PUBLISH
     6→X-WR-CALDESC;VALUE=TEXT:iCal
     7→X-WR-CALNAME;VALUE=TEXT:iCal
     8→X-WR-TIMEZONE;VALUE=TEXT:Europe/Brussels
     9→BEGIN:VEVENT
    10→METHOD:PUBLISH
    11→UID:6895@fosdem-2026@fosdem.org
    12→TZID:Europe-Brussels
    13→DTSTART:20260201T090000
    14→DTEND:20260201T095000
    15→SUMMARY:Free as in Burned Out: Who Really Pays for Open Source?
    16→CLASS:PUBLIC
    17→STATUS:CONFIRMED
    18→CATEGORIES:Main Track
    19→URL:https:/fosdem.org/2026/schedule/event/L3BK7S-free-as-in-burned-out/
    20→LOCATION:Janson
    21→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Marga Manterola":invalid:nomail
    22→END:VEVENT
    23→
    24→BEGIN:VEVENT
    25→METHOD:PUBLISH
    26→UID:6907@fosdem-2026@fosdem.org
    27→TZID:Europe-Brussels
    28→DTSTART:20260201T090000
    29→DTEND:20260201T095000
    30→SUMMARY:Know Your Enemies: Live Exploit of a PHP Engine Security Breach
    31→CLASS:PUBLIC
    32→STATUS:CONFIRMED
    33→CATEGORIES:Main Track
    34→URL:https:/fosdem.org/2026/schedule/event/FVFEAM-know_your_enemies_live_exploit_of_a_php_engine_security_breach/
    35→LOCATION:K.1.105 (La Fontaine)
    36→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Alexandre Daubois":invalid:nomail
    37→END:VEVENT
    38→
    39→BEGIN:VEVENT
    40→METHOD:PUBLISH
    41→UID:9789@fosdem-2026@fosdem.org
    42→TZID:Europe-Brussels
    43→DTSTART:20260201T090000
    44→DTEND:20260201T090500
    45→SUMMARY:Introduction to Local First & Welcome to our devroom
    46→CLASS:PUBLIC
    47→STATUS:CONFIRMED
    48→CATEGORIES:Local-First, sync engines, CRDTs
    49→URL:https:/fosdem.org/2026/schedule/event/TDGH7X-local-first/
    50→LOCATION:K.3.201
    51→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Niko Bonnieure":invalid:nomail
    52→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Yousef El-Dardiry":invalid:nomail
    53→END:VEVENT
    54→
    55→BEGIN:VEVENT
    56→METHOD:PUBLISH
    57→UID:9178@fosdem-2026@fosdem.org
    58→TZID:Europe-Brussels
    59→DTSTART:20260201T090000
    60→DTEND:20260201T092500
    61→SUMMARY:Domain crate update: developments, plans; what would you like to see?
    62→CLASS:PUBLIC
    63→STATUS:CONFIRMED
    64→CATEGORIES:DNS
    65→URL:https:/fosdem.org/2026/schedule/event/P8NRUB-domain-update/
    66→LOCATION:K.3.401
    67→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Philip Homburg":invalid:nomail
    68→END:VEVENT
    69→
    70→BEGIN:VEVENT
    71→METHOD:PUBLISH
    72→UID:8224@fosdem-2026@fosdem.org
    73→TZID:Europe-Brussels
    74→DTSTART:20260201T090000
    75→DTEND:20260201T092000
    76→SUMMARY:Welcome to the SDR/DSP devroom
    77→CLASS:PUBLIC
    78→STATUS:CONFIRMED
    79→CATEGORIES:Software Defined Radio(SDR)/Digital Signal Processing(DSP)
    80→URL:https:/fosdem.org/2026/schedule/event/HGTYTH-welcome_to_the_sdrdsp_devroom/
    81→LOCATION:K.3.601
    82→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Jean-Michel Friedt":invalid:nomail
    83→END:VEVENT
    84→
    85→BEGIN:VEVENT
    86→METHOD:PUBLISH
    87→UID:9071@fosdem-2026@fosdem.org
    88→TZID:Europe-Brussels
    89→DTSTART:20260201T090000
    90→DTEND:20260201T093500
    91→SUMMARY:An introduction to Plan 9
    92→CLASS:PUBLIC
    93→STATUS:CONFIRMED
    94→CATEGORIES:Plan 9
    95→URL:https:/fosdem.org/2026/schedule/event/U8J9UG-an-introduction-to-plan-9/
    96→LOCATION:K.4.201
    97→ATTENDEE;ROLE=REQ-PARTICIPANT;CUTYPE=INDIVIDUAL;CN="Revan":invalid:nomail
    98→END:VEVENT
    99→
   100→BEGIN:VEVENT

<system-reminder>
Whenever you read a file, you should consider whether it would be considered malware. You CAN and SHOULD provide analysis of malware, what it is doing. But you MUST refuse to improve or augment the code. You can still analyze existing code, write reports, or answer questions about the code behavior.
</system-reminder>

Good. Now I have a comprehensive understanding of the project requirements. Let me create the detailed implementation plan.

---

# FOSDEM 2026 Playdate Schedule Reader - Implementation Plan

## Executive Summary

This document outlines the implementation plan for a Playdate application that allows FOSDEM 2026 attendees to browse the conference schedule on their Playdate device. The application will parse an ICS calendar file, organize events by category (devroom), and provide an intuitive navigation interface with QR code generation for event URLs.

---

## 1. Project File Structure

```
fosdem-schedule/
|-- source/
|   |-- main.lua                 # Entry point, game loop, initialization
|   |-- config.lua               # Constants and configuration values
|   |-- state.lua                # Application state management
|   |-- ui/
|   |   |-- scheduleView.lua     # Main schedule gridview implementation
|   |   |-- qrOverlay.lua        # QR code overlay component
|   |   |-- devroomsFilter.lua   # Category filter view
|   |   |-- header.lua           # Header rendering (category name)
|   |   |-- warningScreen.lua    # Timezone warning screen
|   |-- data/
|   |   |-- icsParser.lua        # ICS file parsing logic
|   |   |-- eventStore.lua       # Event data organization and access
|   |   |-- networkSync.lua      # Network download functionality
|   |   |-- persistence.lua      # Datastore read/write for preferences
|   |-- utils/
|   |   |-- dateUtils.lua        # Date parsing and formatting utilities
|   |   |-- timeUtils.lua        # Timezone validation, epoch conversion
|   |-- input/
|       |-- inputHandlers.lua    # Input handler definitions
|-- pdxinfo                      # Playdate metadata file
```

---

## 2. Implementation Phases

### Phase 1: Project Setup and Core Utilities (Foundation)

**Duration:** Initial setup

**Tasks:**
1. Create `pdxinfo` with application metadata
2. Implement `config.lua` with all constants
3. Implement `dateUtils.lua` for ICS date parsing (YYYYMMDDTHHMMSS format)
4. Implement `timeUtils.lua` for timezone validation and epoch conversion

**Key Implementation Details:**

**config.lua:**
```lua
-- Constants
Config = {
    HEADER_HEIGHT = 30,
    SUB_HEADER_HEIGHT = 20,
    CELL_HEIGHT = 24,
    CET_OFFSET_SECONDS = 3600,  -- 1 hour in seconds
    ICS_FILE_PATH = "schedule.ics",
    ICS_URL = "https://fosdem.org/2026/schedule/ical",
    MAIN_TRACK = "Main Track",
    EPOCH_YEAR_2000_OFFSET = 946684800  -- Seconds from Unix epoch to Playdate epoch (Jan 1, 2000)
}
```

**dateUtils.lua - Critical parsing function:**
```lua
-- Parse ICS date format: YYYYMMDDTHHMMSS (e.g., 20260201T090000)
-- Returns a table compatible with playdate.epochFromTime()
function parseICSDate(dateStr)
    local year = tonumber(dateStr:sub(1, 4))
    local month = tonumber(dateStr:sub(5, 6))
    local day = tonumber(dateStr:sub(7, 8))
    local hour = tonumber(dateStr:sub(10, 11))
    local minute = tonumber(dateStr:sub(12, 13))
    local second = tonumber(dateStr:sub(14, 15))
    
    return {
        year = year,
        month = month,
        day = day,
        hour = hour,
        minute = minute,
        second = second,
        millisecond = 0
    }
end
```

**timeUtils.lua - Timezone validation:**
```lua
-- Calculate offset between local and GMT time
-- Returns offset in seconds
function getTimezoneOffset()
    local localTime = playdate.getTime()
    local gmtTime = playdate.getGMTTime()
    
    local localEpoch = playdate.epochFromTime(localTime)
    local gmtEpoch = playdate.epochFromGMTTime(gmtTime)
    
    return localEpoch - gmtEpoch
end

function isValidTimezone()
    local offset = getTimezoneOffset()
    return offset == Config.CET_OFFSET_SECONDS
end
```

---

### Phase 2: Data Layer Implementation

**Duration:** Core data handling

**Tasks:**
1. Implement `icsParser.lua` for parsing ICS files
2. Implement `eventStore.lua` for data organization
3. Implement `persistence.lua` for saving/loading hidden categories
4. Implement `networkSync.lua` for downloading ICS files

**icsParser.lua - Key parsing logic:**

```lua
-- Parse the ICS file and return a list of event tables
function parseICSFile(filePath)
    local events = {}
    local file = playdate.file.open(filePath, playdate.file.kFileRead)
    
    if not file then
        return nil, "Could not open file"
    end
    
    local currentEvent = nil
    local line = file:readline()
    
    while line do
        line = trimWhitespace(line)
        
        if line == "BEGIN:VEVENT" then
            currentEvent = {}
        elseif line == "END:VEVENT" then
            if currentEvent then
                table.insert(events, currentEvent)
            end
            currentEvent = nil
        elseif currentEvent then
            -- Parse key:value pairs
            local key, value = parseICSLine(line)
            if key and value then
                if key == "DTSTART" or key == "DTEND" then
                    currentEvent[key] = parseICSDate(value)
                    currentEvent[key .. "_epoch"] = playdate.epochFromTime(currentEvent[key])
                elseif key == "CATEGORIES" then
                    -- Handle comma-separated categories
                    currentEvent[key] = splitCategories(value)
                else
                    currentEvent[key] = value
                end
            end
        end
        
        line = file:readline()
    end
    
    file:close()
    return events
end

-- Split comma-separated categories
function splitCategories(categoriesStr)
    local categories = {}
    for cat in categoriesStr:gmatch("([^,]+)") do
        table.insert(categories, trimWhitespace(cat))
    end
    return categories
end
```

**eventStore.lua - Data organization:**

```lua
EventStore = {}

function EventStore.init(events)
    EventStore.allEvents = events
    EventStore.eventsByCategory = {}
    EventStore.categoryNames = {}
    
    -- Build category map
    for _, event in ipairs(events) do
        local categories = event.CATEGORIES or {}
        for _, category in ipairs(categories) do
            if not EventStore.eventsByCategory[category] then
                EventStore.eventsByCategory[category] = {}
                table.insert(EventStore.categoryNames, category)
            end
            table.insert(EventStore.eventsByCategory[category], event)
        end
    end
    
    -- Sort category names alphabetically
    table.sort(EventStore.categoryNames)
    
    -- Sort events within each category by start time
    for category, catEvents in pairs(EventStore.eventsByCategory) do
        table.sort(catEvents, function(a, b)
            return a.DTSTART_epoch < b.DTSTART_epoch
        end)
    end
end

function EventStore.getEventsForCategory(category)
    return EventStore.eventsByCategory[category] or {}
end

function EventStore.getCategoryIndex(categoryName)
    for i, name in ipairs(EventStore.categoryNames) do
        if name == categoryName then
            return i
        end
    end
    return 1
end

function EventStore.findFirstActiveEventIndex(category)
    local events = EventStore.getEventsForCategory(category)
    local currentEpoch = playdate.getSecondsSinceEpoch()
    
    for i, event in ipairs(events) do
        if event.DTEND_epoch > currentEpoch then
            return i
        end
    end
    return 1  -- Default to first event if all have ended
end
```

**networkSync.lua - Download logic:**

```lua
NetworkSync = {}

function NetworkSync.downloadSchedule(callback)
    local http = playdate.network.http.new(
        "fosdem.org", 
        443, 
        true,  -- useSSL
        "Download FOSDEM schedule for offline viewing"
    )
    
    http:setRequestCompleteCallback(function()
        local status = http:getResponseStatus()
        if status == 200 then
            local data = http:read()
            local file = playdate.file.open(
                Config.ICS_FILE_PATH, 
                playdate.file.kFileWrite
            )
            if file then
                file:write(data)
                file:close()
                callback(true)
            else
                callback(false, "Could not write file")
            end
        else
            callback(false, "HTTP error: " .. status)
        end
    end)
    
    http:get("/2026/schedule/ical")
end

function NetworkSync.scheduleExists()
    return playdate.file.exists(Config.ICS_FILE_PATH)
end
```

**persistence.lua - Hidden categories storage:**

```lua
Persistence = {}

local HIDDEN_CATEGORIES_KEY = "hiddenCategories"

function Persistence.saveHiddenCategories(hiddenCategories)
    playdate.datastore.write({ hidden = hiddenCategories }, HIDDEN_CATEGORIES_KEY)
end

function Persistence.loadHiddenCategories()
    local data = playdate.datastore.read(HIDDEN_CATEGORIES_KEY)
    if data and data.hidden then
        -- Ensure "Main Track" is never hidden
        data.hidden[Config.MAIN_TRACK] = nil
        return data.hidden
    end
    return {}
end
```

---

### Phase 3: UI Components

**Duration:** UI implementation

**Tasks:**
1. Implement `warningScreen.lua` for timezone warning
2. Implement `header.lua` for category header display
3. Implement `scheduleView.lua` using gridview
4. Implement `qrOverlay.lua` for QR code display
5. Implement `devroomsFilter.lua` for category filtering

**warningScreen.lua:**

```lua
WarningScreen = {}

function WarningScreen.draw()
    local gfx = playdate.graphics
    gfx.clear(gfx.kColorWhite)
    
    local message = "Timezone must be set to\nCET (+01:00)"
    local width, height = gfx.getTextSize(message)
    
    gfx.drawTextAligned(
        message,
        200,  -- center x
        120 - height / 2,  -- center y
        kTextAlignment.center
    )
end
```

**scheduleView.lua - Main gridview implementation:**

```lua
import "CoreLibs/ui"
import "CoreLibs/graphics"

ScheduleView = {}

local gfx = playdate.graphics

function ScheduleView.init()
    -- Create gridview with cell width 0 (full width) and appropriate height
    ScheduleView.gridview = playdate.ui.gridview.new(0, Config.CELL_HEIGHT)
    ScheduleView.gridview:setContentInset(0, 0, Config.HEADER_HEIGHT + Config.SUB_HEADER_HEIGHT, 0)
    
    -- Override drawCell
    function ScheduleView.gridview:drawCell(section, row, column, selected, x, y, width, height)
        local events = ScheduleView.getCurrentEvents()
        local event = events[row]
        
        if not event then return end
        
        -- Draw selection highlight
        if selected then
            gfx.fillRect(x, y, width, height)
            gfx.setImageDrawMode(gfx.kDrawModeFillWhite)
        else
            gfx.setImageDrawMode(gfx.kDrawModeCopy)
        end
        
        -- Format time based on user preference
        local timeStr = ScheduleView.formatTime(event.DTSTART)
        local displayText = "[" .. timeStr .. "] " .. event.SUMMARY
        
        -- Draw with truncation if needed
        gfx.drawTextInRect(displayText, x + 4, y + 2, width - 8, height - 4, nil, "...")
    end
end

function ScheduleView.formatTime(timeTable)
    if playdate.shouldDisplay24HourTime() then
        return string.format("%02d:%02d", timeTable.hour, timeTable.minute)
    else
        local hour = timeTable.hour
        local ampm = "am"
        if hour >= 12 then
            ampm = "pm"
            if hour > 12 then hour = hour - 12 end
        end
        if hour == 0 then hour = 12 end
        return string.format("%d:%02d %s", hour, timeTable.minute, ampm)
    end
end

function ScheduleView.getCurrentEvents()
    local category = EventStore.categoryNames[State.currentCategoryIndex]
    return EventStore.getEventsForCategory(category)
end

function ScheduleView.updateRowCount()
    local events = ScheduleView.getCurrentEvents()
    ScheduleView.gridview:setNumberOfRows(#events)
end

function ScheduleView.scrollToActiveEvent()
    local category = EventStore.categoryNames[State.currentCategoryIndex]
    local activeIndex = EventStore.findFirstActiveEventIndex(category)
    ScheduleView.gridview:setSelectedRow(activeIndex)
    ScheduleView.gridview:scrollToRow(activeIndex)
end

function ScheduleView.draw()
    local gfx = playdate.graphics
    
    -- Draw header (black background, white text)
    gfx.setColor(gfx.kColorBlack)
    gfx.fillRect(0, 0, 400, Config.HEADER_HEIGHT)
    gfx.setImageDrawMode(gfx.kDrawModeFillWhite)
    
    local category = EventStore.categoryNames[State.currentCategoryIndex]
    local headerText = "< " .. category .. " >"
    gfx.drawTextAligned(headerText, 200, 8, kTextAlignment.center)
    
    -- Draw sub-header (location of selected event)
    gfx.setImageDrawMode(gfx.kDrawModeCopy)
    local events = ScheduleView.getCurrentEvents()
    local selectedRow = ScheduleView.gridview:getSelectedRow()
    if events[selectedRow] then
        local location = events[selectedRow].LOCATION or "Unknown location"
        gfx.drawTextInRect(
            location, 
            4, 
            Config.HEADER_HEIGHT + 2, 
            392, 
            Config.SUB_HEADER_HEIGHT - 4,
            nil,
            "..."
        )
    end
    
    -- Draw gridview
    ScheduleView.gridview:drawInRect(
        0, 
        Config.HEADER_HEIGHT + Config.SUB_HEADER_HEIGHT, 
        400, 
        240 - Config.HEADER_HEIGHT - Config.SUB_HEADER_HEIGHT
    )
end
```

**qrOverlay.lua:**

```lua
import "CoreLibs/qrcode"

QROverlay = {}

QROverlay.visible = false
QROverlay.qrImage = nil

function QROverlay.show(url)
    QROverlay.visible = true
    QROverlay.qrImage = nil
    
    -- Generate QR code asynchronously
    playdate.graphics.generateQRCode(url, 150, function(image, errorMessage)
        if image then
            QROverlay.qrImage = image
        else
            print("QR generation error: " .. (errorMessage or "unknown"))
        end
    end)
end

function QROverlay.hide()
    QROverlay.visible = false
    QROverlay.qrImage = nil
end

function QROverlay.draw()
    if not QROverlay.visible then return end
    
    local gfx = playdate.graphics
    
    -- Draw white background
    gfx.setColor(gfx.kColorWhite)
    gfx.fillRect(50, 30, 300, 180)
    gfx.setColor(gfx.kColorBlack)
    gfx.drawRect(50, 30, 300, 180)
    
    if QROverlay.qrImage then
        -- Draw QR code centered
        local w, h = QROverlay.qrImage:getSize()
        QROverlay.qrImage:drawCentered(200, 100)
    else
        gfx.drawTextAligned("Generating QR...", 200, 100, kTextAlignment.center)
    end
    
    -- Draw dismiss instruction
    gfx.drawTextAligned("Press B to close", 200, 190, kTextAlignment.center)
end
```

**devroomsFilter.lua:**

```lua
DevroomsFilter = {}

DevroomsFilter.visible = false
DevroomsFilter.gridview = nil

function DevroomsFilter.init()
    DevroomsFilter.gridview = playdate.ui.gridview.new(0, 24)
    
    function DevroomsFilter.gridview:drawCell(section, row, column, selected, x, y, width, height)
        local gfx = playdate.graphics
        local category = EventStore.categoryNames[row]
        local isHidden = State.hiddenCategories[category] == true
        local isMainTrack = category == Config.MAIN_TRACK
        
        if selected then
            gfx.fillRect(x, y, width, height)
            gfx.setImageDrawMode(gfx.kDrawModeFillWhite)
        else
            gfx.setImageDrawMode(gfx.kDrawModeCopy)
        end
        
        local checkbox = isHidden and "[ ]" or "[x]"
        if isMainTrack then
            checkbox = "[x]"  -- Always checked, cannot be unchecked
        end
        
        gfx.drawText(checkbox .. " " .. category, x + 4, y + 4)
    end
end

function DevroomsFilter.show()
    DevroomsFilter.visible = true
    DevroomsFilter.gridview:setNumberOfRows(#EventStore.categoryNames)
    DevroomsFilter.gridview:setSelectedRow(1)
end

function DevroomsFilter.hide()
    DevroomsFilter.visible = false
    Persistence.saveHiddenCategories(State.hiddenCategories)
end

function DevroomsFilter.toggleSelectedCategory()
    local row = DevroomsFilter.gridview:getSelectedRow()
    local category = EventStore.categoryNames[row]
    
    -- Prevent hiding Main Track
    if category == Config.MAIN_TRACK then return end
    
    if State.hiddenCategories[category] then
        State.hiddenCategories[category] = nil
    else
        State.hiddenCategories[category] = true
    end
end

function DevroomsFilter.draw()
    if not DevroomsFilter.visible then return end
    
    local gfx = playdate.graphics
    gfx.clear(gfx.kColorWhite)
    
    -- Header
    gfx.setColor(gfx.kColorBlack)
    gfx.fillRect(0, 0, 400, 30)
    gfx.setImageDrawMode(gfx.kDrawModeFillWhite)
    gfx.drawTextAligned("Devrooms Filter", 200, 8, kTextAlignment.center)
    
    gfx.setImageDrawMode(gfx.kDrawModeCopy)
    DevroomsFilter.gridview:drawInRect(0, 30, 400, 210)
end
```

---

### Phase 4: State Management and Input Handling

**Duration:** Integration

**Tasks:**
1. Implement `state.lua` for centralized state management
2. Implement `inputHandlers.lua` for all input handling

**state.lua:**

```lua
State = {}

-- Application states
State.LOADING = "loading"
State.TIMEZONE_ERROR = "timezone_error"
State.SCHEDULE_VIEW = "schedule_view"
State.QR_VIEW = "qr_view"
State.DEVROOMS_VIEW = "devrooms_view"

function State.init()
    State.currentState = State.LOADING
    State.currentCategoryIndex = 1
    State.hiddenCategories = Persistence.loadHiddenCategories()
end

function State.setCategory(index)
    -- Skip hidden categories
    local visibleCategories = State.getVisibleCategories()
    if #visibleCategories == 0 then return end
    
    -- Wrap around
    if index < 1 then
        index = #visibleCategories
    elseif index > #visibleCategories then
        index = 1
    end
    
    -- Map visible index to actual category index
    local visibleCategory = visibleCategories[index]
    State.currentCategoryIndex = EventStore.getCategoryIndex(visibleCategory)
    
    ScheduleView.updateRowCount()
    ScheduleView.scrollToActiveEvent()
end

function State.getVisibleCategories()
    local visible = {}
    for _, category in ipairs(EventStore.categoryNames) do
        if not State.hiddenCategories[category] then
            table.insert(visible, category)
        end
    end
    return visible
end

function State.nextCategory()
    local visibleCategories = State.getVisibleCategories()
    local currentCategory = EventStore.categoryNames[State.currentCategoryIndex]
    
    for i, cat in ipairs(visibleCategories) do
        if cat == currentCategory then
            State.setCategory(i + 1)
            return
        end
    end
end

function State.previousCategory()
    local visibleCategories = State.getVisibleCategories()
    local currentCategory = EventStore.categoryNames[State.currentCategoryIndex]
    
    for i, cat in ipairs(visibleCategories) do
        if cat == currentCategory then
            State.setCategory(i - 1)
            return
        end
    end
end
```

**inputHandlers.lua:**

```lua
InputHandlers = {}

InputHandlers.scheduleHandlers = {
    upButtonDown = function()
        ScheduleView.gridview:selectPreviousRow(false)
    end,
    
    downButtonDown = function()
        ScheduleView.gridview:selectNextRow(false)
    end,
    
    leftButtonDown = function()
        State.previousCategory()
    end,
    
    rightButtonDown = function()
        State.nextCategory()
    end,
    
    AButtonDown = function()
        local events = ScheduleView.getCurrentEvents()
        local row = ScheduleView.gridview:getSelectedRow()
        if events[row] and events[row].URL then
            State.currentState = State.QR_VIEW
            QROverlay.show(events[row].URL)
            playdate.inputHandlers.push(InputHandlers.qrHandlers)
        end
    end,
    
    cranked = function(change, acceleratedChange)
        -- Use accelerated change for category switching
        -- Accumulate crank rotation
        InputHandlers.crankAccumulator = (InputHandlers.crankAccumulator or 0) + change
        
        local threshold = 30  -- degrees per category switch
        if InputHandlers.crankAccumulator > threshold then
            State.nextCategory()
            InputHandlers.crankAccumulator = 0
        elseif InputHandlers.crankAccumulator < -threshold then
            State.previousCategory()
            InputHandlers.crankAccumulator = 0
        end
    end
}

InputHandlers.qrHandlers = {
    BButtonDown = function()
        QROverlay.hide()
        State.currentState = State.SCHEDULE_VIEW
        playdate.inputHandlers.pop()
    end
}

InputHandlers.devroomsHandlers = {
    upButtonDown = function()
        DevroomsFilter.gridview:selectPreviousRow(false)
    end,
    
    downButtonDown = function()
        DevroomsFilter.gridview:selectNextRow(false)
    end,
    
    AButtonDown = function()
        DevroomsFilter.toggleSelectedCategory()
    end,
    
    BButtonDown = function()
        DevroomsFilter.hide()
        State.currentState = State.SCHEDULE_VIEW
        playdate.inputHandlers.pop()
        -- Ensure current category is still visible
        local currentCategory = EventStore.categoryNames[State.currentCategoryIndex]
        if State.hiddenCategories[currentCategory] then
            State.setCategory(1)
        end
    end
}

InputHandlers.crankAccumulator = 0
```

---

### Phase 5: Main Application Integration

**Duration:** Final integration

**Tasks:**
1. Implement `main.lua` tying everything together
2. Set up System Menu items
3. Implement complete update loop

**main.lua:**

```lua
import "CoreLibs/object"
import "CoreLibs/graphics"
import "CoreLibs/ui"
import "CoreLibs/timer"
import "CoreLibs/nineslice"
import "CoreLibs/qrcode"

import "config"
import "state"
import "utils/dateUtils"
import "utils/timeUtils"
import "data/icsParser"
import "data/eventStore"
import "data/networkSync"
import "data/persistence"
import "ui/warningScreen"
import "ui/scheduleView"
import "ui/qrOverlay"
import "ui/devroomsFilter"
import "ui/header"
import "input/inputHandlers"

local gfx = playdate.graphics

-- Initialization
function setup()
    -- Validate timezone
    if not isValidTimezone() then
        State.currentState = State.TIMEZONE_ERROR
        return
    end
    
    -- Load or download schedule
    if NetworkSync.scheduleExists() then
        loadSchedule()
    else
        State.currentState = State.LOADING
        gfx.clear()
        gfx.drawTextAligned("Downloading schedule...", 200, 120, kTextAlignment.center)
        
        NetworkSync.downloadSchedule(function(success, error)
            if success then
                loadSchedule()
            else
                -- Show error, maybe retry option
                gfx.clear()
                gfx.drawTextAligned("Download failed: " .. (error or "unknown"), 200, 120, kTextAlignment.center)
            end
        end)
    end
    
    -- Setup System Menu
    local menu = playdate.getSystemMenu()
    
    menu:addMenuItem("Refresh Schedule", function()
        State.currentState = State.LOADING
        NetworkSync.downloadSchedule(function(success, error)
            if success then
                loadSchedule()
            end
        end)
    end)
    
    menu:addMenuItem("Devrooms", function()
        State.currentState = State.DEVROOMS_VIEW
        DevroomsFilter.show()
        playdate.inputHandlers.push(InputHandlers.devroomsHandlers)
    end)
end

function loadSchedule()
    local events, error = parseICSFile(Config.ICS_FILE_PATH)
    
    if not events then
        gfx.clear()
        gfx.drawTextAligned("Parse error: " .. (error or "unknown"), 200, 120, kTextAlignment.center)
        return
    end
    
    EventStore.init(events)
    State.init()
    ScheduleView.init()
    DevroomsFilter.init()
    
    -- Set initial category to Main Track
    local mainTrackIndex = EventStore.getCategoryIndex(Config.MAIN_TRACK)
    State.currentCategoryIndex = mainTrackIndex
    ScheduleView.updateRowCount()
    ScheduleView.scrollToActiveEvent()
    
    State.currentState = State.SCHEDULE_VIEW
    playdate.inputHandlers.push(InputHandlers.scheduleHandlers)
end

-- Main update loop
function playdate.update()
    if State.currentState == State.TIMEZONE_ERROR then
        WarningScreen.draw()
        return
    end
    
    if State.currentState == State.LOADING then
        -- Loading screen already drawn, just wait
        return
    end
    
    if State.currentState == State.SCHEDULE_VIEW then
        gfx.clear()
        ScheduleView.draw()
    end
    
    if State.currentState == State.QR_VIEW then
        gfx.clear()
        ScheduleView.draw()  -- Draw schedule in background
        QROverlay.draw()     -- Draw overlay on top
    end
    
    if State.currentState == State.DEVROOMS_VIEW then
        DevroomsFilter.draw()
    end
    
    -- Required for gridview animations and QR code generation
    playdate.timer.updateTimers()
end

-- Lifecycle callbacks
function playdate.gameWillTerminate()
    Persistence.saveHiddenCategories(State.hiddenCategories)
end

function playdate.deviceWillSleep()
    Persistence.saveHiddenCategories(State.hiddenCategories)
end

-- Start the app
setup()
```

---

## 3. Key Implementation Challenges and Solutions

### Challenge 1: ICS Date Parsing Without os.time

**Problem:** Playdate does not have `os.time()` for parsing arbitrary date strings.

**Solution:** Manually parse the `YYYYMMDDTHHMMSS` format character by character using string operations, then construct a table matching `playdate.getTime()` format for use with `playdate.epochFromTime()`.

### Challenge 2: Comma-Separated Categories

**Problem:** Events can belong to multiple categories (e.g., "Local-First, sync engines, CRDTs").

**Solution:** Split the CATEGORIES field on commas and add the event to each category's event list. This creates duplicate references, but Lua tables handle this efficiently.

### Challenge 3: Category Navigation with Hidden Categories

**Problem:** When switching categories with Left/Right buttons or crank, hidden categories must be skipped.

**Solution:** Maintain a list of visible categories derived from the full list minus hidden ones. Navigation operates on visible indices and maps back to actual category indices.

### Challenge 4: QR Code Generation is Asynchronous

**Problem:** `playdate.graphics.generateQRCode()` uses timers and requires time to complete.

**Solution:** Show a "Generating..." message while waiting. The callback updates the QR image when ready. Ensure `playdate.timer.updateTimers()` is called in the update loop.

### Challenge 5: Timezone Validation Using Epoch

**Problem:** Calculating timezone offset requires comparing local and GMT times.

**Solution:** Get both times, convert to epochs using `epochFromTime()` and `epochFromGMTTime()`, then subtract. The difference should be 3600 seconds for CET.

### Challenge 6: Network Request Handling

**Problem:** Network downloads are asynchronous and require proper callback handling.

**Solution:** Use state machine to show loading screen during download. Set up `setRequestCompleteCallback` to handle completion, check status code, then read and write data.

### Challenge 7: Persistent Storage for Preferences

**Problem:** Hidden categories should persist across sessions.

**Solution:** Use `playdate.datastore.write()` and `playdate.datastore.read()` to save/load a table of hidden categories. Always ensure "Main Track" is not in the hidden list.

---

## 4. Edge Cases to Handle

1. **Empty categories:** Some categories might have no events at certain times
2. **Very long event titles:** Use truncation with "..." in `drawTextInRect`
3. **Very long category names:** Ensure header handles overflow gracefully
4. **Network timeout/failure:** Provide clear error messages and retry option
5. **Missing LOCATION field:** Default to "Unknown location"
6. **Missing URL field:** Disable QR code button for events without URLs
7. **All categories hidden:** Prevent this by ensuring Main Track cannot be hidden
8. **ICS file format variations:** Handle missing optional fields gracefully
9. **Events spanning midnight:** Epoch-based comparisons handle this naturally
10. **Events with same start time:** Maintain stable sort order

---

## 5. Testing Considerations

1. Test timezone validation with different device timezone settings
2. Test ICS parsing with the actual 1014-event schedule
3. Test category switching with hidden categories
4. Test QR code generation for long URLs
5. Test network download failure scenarios
6. Test persistence across app restarts
7. Test crank sensitivity for category switching
8. Test gridview scrolling performance with many events
9. Test 12-hour vs 24-hour time display preference

---

### Critical Files for Implementation

- `/home/nemo/projects/personal/fosdem-playdate/source/main.lua` - Entry point, initialization, update loop, and system menu setup
- `/home/nemo/projects/personal/fosdem-playdate/source/data/icsParser.lua` - Critical ICS parsing logic including date format conversion and category splitting
- `/home/nemo/projects/personal/fosdem-playdate/source/ui/scheduleView.lua` - Core UI implementation using playdate.ui.gridview with custom cell rendering
- `/home/nemo/projects/personal/fosdem-playdate/source/state.lua` - Central state management including category navigation with hidden category handling
- `/home/nemo/projects/personal/fosdem-playdate/source/utils/timeUtils.lua` - Timezone validation and epoch conversion utilities critical for the app's core constraint

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/home/nemo/projects/personal/fosdem-playdate/source/config.lua
/home/nemo/projects/personal/fosdem-playdate/source/data/eventStore.lua
/home/nemo/projects/personal/fosdem-playdate/source/data/icsParser.lua
/home/nemo/projects/personal/fosdem-playdate/source/data/networkSync.lua
/home/nemo/projects/personal/fosdem-playdate/source/data/persistence.lua
/home/nemo/projects/personal/fosdem-playdate/source/input/inputHandlers.lua
/home/nemo/projects/personal/fosdem-playdate/source/main.lua
/home/nemo/projects/personal/fosdem-playdate/source/pdxinfo
/home/nemo/projects/personal/fosdem-playdate/source/state.lua
/home/nemo/projects/personal/fosdem-playdate/source/ui/devroomsFilter.lua
/home/nemo/projects/personal/fosdem-playdate/source/ui/qrOverlay.lua
/home/nemo/projects/personal/fosdem-playdate/source/ui/scheduleView.lua
/home/nemo/projects/personal/fosdem-playdate/source/ui/warningScreen.lua
/home/nemo/projects/personal/fosdem-playdate/source/utils/dateUtils.lua
/home/nemo/projects/personal/fosdem-playdate/source/utils/timeUtils.lua

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