# Building GemReader

This document provides detailed instructions on how to build the GemReader application for different platforms, with a focus on creating executable files (especially .exe files for Windows).

## Prerequisites

Before building GemReader, ensure you have the following installed:

- Go 1.24 or higher
- Git (for cloning the repository)
- A terminal/command prompt
- For Windows: A modern version of Windows that supports Go compilation

## Building for Windows (.exe)

### Basic Build

To build the application for Windows and create an .exe file, run the following command:

```bash
go build -o gemreader.exe cmd/gemreader/main.go
```

This will create a `gemreader.exe` file in your current directory.

### Cross-compilation from Other Platforms

If you're building from a non-Windows platform (Linux or macOS) and want to create a Windows executable, use these commands:

```bash
GOOS=windows GOARCH=amd64 go build -o gemreader.exe cmd/gemreader/main.go
```

### Advanced Build Options

#### Building with release flags (optimized)

For a more optimized build with smaller file size:

```bash
go build -ldflags "-s -w" -o gemreader.exe cmd/gemreader/main.go
```

- `-s`: Omit the symbol table and debug information
- `-w`: Omit the DWARF symbol table

#### Building with version information

To embed version information in the executable:

```bash
go build -ldflags "-X main.Version=1.0.0 -s -w" -o gemreader.exe cmd/gemreader/main.go
```

## Building for Other Platforms

This section covers building the application on Windows for other operating systems using Go's cross-compilation feature.

### From Windows to Linux

To build for Linux from a Windows machine, you have several options:

**Option 1: Using PowerShell (Recommended)**

```powershell
# For 64-bit Linux
$env:GOOS="linux"; $env:GOARCH="amd64"; go build -o gemreader-linux cmd/gemreader/main.go

# For 32-bit Linux  
$env:GOOS="linux"; $env:GOARCH="386"; go build -o gemreader-linux-386 cmd/gemreader/main.go

# For ARM64 Linux
$env:GOOS="linux"; $env:GOARCH="arm64"; go build -o gemreader-linux-arm64 cmd/gemreader/main.go
```

**Option 2: Using Command Prompt (CMD)**
In Command Prompt, you need to set the environment variables persistently for the session:

```batch
go env -w GOOS=linux
go env -w GOARCH=amd64
go build -o gemreader-linux cmd/gemreader/main.go

# Reset to default after building
go env -w GOOS=windows
go env -w GOARCH=amd64
```

**Option 3: Temporary environment variables in PowerShell (One-liner)**

```powershell
$env:GOOS="linux"; $env:GOARCH="amd64"; go build -o gemreader-linux cmd/gemreader/main.go; $env:GOOS="windows"; $env:GOARCH="amd64"
```

### From Windows to macOS

To build for macOS from a Windows machine:

**Using PowerShell:**

```powershell
# For Intel-based Macs
$env:GOOS="darwin"; $env:GOARCH="amd64"; go build -o gemreader-mac cmd/gemreader/main.go

# For Apple Silicon Macs (M1/M2/M3)
$env:GOOS="darwin"; $env:GOARCH="arm64"; go build -o gemreader-mac-arm64 cmd/gemreader/main.go
```

**Using Command Prompt:**

```batch
go env -w GOOS=darwin
go env -w GOARCH=amd64
go build -o gemreader-mac cmd/gemreader/main.go

# Reset to default after building
go env -w GOOS=windows
go env -w GOARCH=amd64
```

### Using PowerShell

If you're using PowerShell instead of Command Prompt, the syntax is slightly different:

```powershell
# For Linux ARM64
$env:GOOS="linux"; $env:GOARCH="arm64"; go build -o gemreader-linux-arm64 cmd/gemreader/main.go

# For macOS
$env:GOOS="darwin"; $env:GOARCH="arm64"; go build -o gemreader-mac-arm64 cmd/gemreader/main.go
```

### Common GOOS and GOARCH Values

| GOOS    | GOARCH | Platform                     |
| ------- | ------ | ---------------------------- |
| windows | amd64  | 64-bit Windows               |
| windows | 386    | 32-bit Windows               |
| windows | arm64  | 64-bit Windows on ARM        |
| linux   | amd64  | 64-bit Linux                 |
| linux   | 386    | 32-bit Linux                 |
| linux   | arm64  | 64-bit Linux on ARM          |
| darwin  | amd64  | 64-bit macOS (Intel)         |
| darwin  | arm64  | 64-bit macOS (Apple Silicon) |

### Building for Multiple Platforms

You can create a batch script to build for multiple platforms at once. Here's an example `build-all.bat`:

```batch
@echo off
echo Building GemReader for multiple platforms...

REM Create dist directory if it doesn't exist
if not exist dist mkdir dist

echo Building for Windows (64-bit)...
go env -w GOOS=windows
go env -w GOARCH=amd64
go build -ldflags "-s -w" -o dist/gemreader-windows-amd64.exe cmd/gemreader/main.go

echo Building for Linux (64-bit)...
go env -w GOOS=linux
go env -w GOARCH=amd64
go build -ldflags "-s -w" -o dist/gemreader-linux-amd64 cmd/gemreader/main.go

echo Building for macOS (Intel)...
go env -w GOOS=darwin
go env -w GOARCH=amd64
go build -ldflags "-s -w" -o dist/gemreader-darwin-amd64 cmd/gemreader/main.go

echo Building for macOS (Apple Silicon)...
go env -w GOOS=darwin
go env -w GOARCH=arm64
go build -ldflags "-s -w" -o dist/gemreader-darwin-arm64 cmd/gemreader/main.go

echo Resetting GOOS and GOARCH to default...
go env -w GOOS=windows
go env -w GOARCH=amd64

echo Build process completed!
pause
```

Alternatively, you can create a PowerShell script `build-all.ps1` for more reliable cross-platform building:

```powershell
Write-Host "Building GemReader for multiple platforms..."

# Create dist directory if it doesn't exist
if (!(Test-Path dist)) {
    New-Item -ItemType Directory -Path dist
}

# Build for Windows
Write-Host "Building for Windows (64-bit)..."
$env:GOOS="windows"
$env:GOARCH="amd64"
go build -ldflags "-s -w" -o dist/gemreader-windows-amd64.exe cmd/gemreader/main.go

# Build for Linux
Write-Host "Building for Linux (64-bit)..."
$env:GOOS="linux"
$env:GOARCH="amd64"
go build -ldflags "-s -w" -o dist/gemreader-linux-amd64 cmd/gemreader/main.go

# Build for macOS Intel
Write-Host "Building for macOS (Intel)..."
$env:GOOS="darwin"
$env:GOARCH="amd64"
go build -ldflags "-s -w" -o dist/gemreader-darwin-amd64 cmd/gemreader/main.go

# Build for macOS Apple Silicon
Write-Host "Building for macOS (Apple Silicon)..."
$env:GOOS="darwin"
$env:GOARCH="arm64"
go build -ldflags "-s -w" -o dist/gemreader-darwin-arm64 cmd/gemreader/main.go

Write-Host "Build process completed!"
```

## Using Build Scripts

For more complex builds, you can create a build script. Here's an example `build.bat` for Windows:

```batch
@echo off
echo Building GemReader for Windows...

REM Build the application
go build -ldflags "-s -w" -o gemreader.exe cmd/gemreader/main.go

if %ERRORLEVEL% == 0 (
    echo Build successful! gemreader.exe has been created.
) else (
    echo Build failed!
    exit /b %ERRORLEVEL%
)
```

And a `build.sh` script for Unix-like systems:

```bash
#!/bin/bash
echo "Building GemReader..."

# Build the application
go build -ldflags "-s -w" -o gemreader cmd/gemreader/main.go

if [ $? -eq 0 ]; then
    echo "Build successful! gemreader has been created."
else
    echo "Build failed!"
    exit 1
fi
```

## Build Targets with Go Releaser (Alternative Approach)

If the project uses GoReleaser or similar tools, you can use:

```bash
# Install GoReleaser if not already installed
go install github.com/goreleaser/goreleaser@latest

# Build all targets defined in .goreleaser.yml
goreleaser build --single-target --snapshot
```

## Troubleshooting Build Issues

### Common Issues

#### Missing Dependencies

If you encounter dependency issues, run:

```bash
go mod tidy
```

This will ensure all dependencies are downloaded and the go.mod file is updated.

#### CGO Issues

If your build fails due to CGO issues (uncommon for this project), you can disable CGO:

```bash
CGO_ENABLED=0 go build -o gemreader.exe cmd/gemreader/main.go
```

#### Large Executable Size

If the resulting executable is too large, consider these options:

1. Use the `-ldflags "-s -w"` options as mentioned above

2. Use UPX to compress the executable (third-party tool):
   
   ```bash
   upx --best gemreader.exe
   ```

### Checking Build Information

To verify your build information, you can use:

```bash
go version -m gemreader.exe
```

This will show build information about the executable.

## Production Builds

For production releases, consider using these flags to create a minimal executable:

```bash
go build \
  -ldflags="-s -w -X main.Version=1.0.0" \
  -o gemreader.exe \
  cmd/gemreader/main.go
```

## Verifying the Build

After building, you can test your executable by running:

```bash
# On Windows
.\gemreader.exe sample.md

# Or with a different markdown file
.\gemreader.exe path\to\your\markdown\file.md
```

## Build Artifacts

The build process will create:

- `gemreader.exe` (or platform-specific executable)
- The executable is self-contained and doesn't require additional files to run
- Configuration files like `config.toml` and `sample.md` can be distributed separately if needed

## Creating an Installer (Optional)

For distribution purposes, you may want to create an installer for Windows using tools like:

- NSIS (Nullsoft Scriptable Install System)
- Inno Setup
- GoReleaser with nfpm for cross-platform packaging

This is outside the scope of this document but worth considering for production releases.