Apply site theme

$siteUrl = "https://contoso.sharepoint.com/sites/DemoSite"

$themePalette = @{
    "palette" = @{
        "themePrimary"= "#1BF242";
        "themeLighterAlt"= "#0d0b00";
        "themeLighter"= "#0b35bc";
        "themeLight"= "#322d00";
        "themeTertiary"= "#6a5f00";
       "themeSecondary"= "#1B22F2";
        "themeDarkAlt"= "#ffe817";
        "themeDark"= "#ffed4b";
        "themeDarker"= "#fff171";
        "neutralLighterAlt"= "#252525";
        "neutralLighter"= "#282828";
        "neutralLight"= "#313131";
        "neutralQuaternaryAlt"= "#3f3f3f";
        "neutralQuaternary"= "#484848";
        "neutralTertiaryAlt"= "#4f4f4f";
        "neutralTertiary"= "#c8c8c8";
        "neutralSecondaryAlt"= "#d0d0d0";
        "neutralSecondary"= "#dadada";
        "neutralPrimary"= "#ffffff";
        "neutralDark"= "#eaeaea";
        "black"= "#f8f8f8";
        "white"= "#1f1f1f";
        "primaryBackground"= "#1f1f1f";
        "primaryText"= "#ffffff";
        "error"= "#ff5f5f"
    }
}

Connect-PnPOnline -Url $siteUrl -ClientId "" -Interactive

$accessToken = Get-PnPAccessToken -ResourceTypeName SharePoint
$bodyObject = @{
    name      = "Sample theme"
    themeJson = ($themePalette | ConvertTo-Json -Depth 10 -Compress)
}

$bodyJson = $bodyObject | ConvertTo-Json -Depth 10

$headers = @{
    "Authorization" = "Bearer $accessToken"
    "Accept"        = "application/json;odata.metadata=minimal"
    "Content-type"  = "application/json; charset=utf-8"
    "ODATA-VERSION" = "4.0"
}

$uri = "$siteUrl/_api/thememanager/Applytheme"

Invoke-RestMethod -Method POST -Uri $uri -Headers $headers -Body $bodyJson

Disconnect-PnPOnline

[CmdletBinding(SupportsShouldProcess = $true)]
param(
    [Parameter(Mandatory, HelpMessage = "SharePoint site URL to apply the theme")]
    [string]$SiteUrl,
    
    [Parameter(Mandatory, HelpMessage = "Path to theme JSON file or inline JSON string")]
    [string]$ThemeJson,
    
    [Parameter(HelpMessage = "Unique name for the temporary theme")]
    [string]$ThemeName = "TempTheme-$(Get-Date -Format 'yyyyMMddHHmmss')",
    
    [Parameter(HelpMessage = "Keep the theme registered in tenant after applying")]
    [switch]$KeepTheme
)

begin {
    m365 login --ensure
    if ($LASTEXITCODE -ne 0) {
        throw "Failed to verify login status"
    }
    
    $themeContent = if ($ThemeJson.StartsWith('@')) {
        $filePath = $ThemeJson.Substring(1)
        if (-not (Test-Path $filePath)) {
            throw "Theme file not found: $filePath"
        }
        Get-Content $filePath -Raw
    } else {
        $ThemeJson
    }
}

process {
    if (-not $PSCmdlet.ShouldProcess($SiteUrl, "Apply theme '$ThemeName'")) {
        return
    }
    
    Write-Host "Registering theme '$ThemeName'..." -ForegroundColor Cyan
    $setResult = m365 spo theme set --name $ThemeName --theme $themeContent 2>&1
    if ($LASTEXITCODE -ne 0) {
        throw "Failed to register theme: $setResult"
    }
    
    Write-Host "Applying theme to: $SiteUrl" -ForegroundColor Cyan
    $applyResult = m365 spo theme apply --name $ThemeName --webUrl $SiteUrl --output json 2>&1
    if ($LASTEXITCODE -ne 0) {
        throw "Failed to apply theme: $applyResult"
    }
    
    Write-Host "Theme applied successfully!" -ForegroundColor Green
    Write-Host "Catalog path: $applyResult" -ForegroundColor Gray
    
    if (-not $KeepTheme) {
        $removeResult = m365 spo theme remove --name $ThemeName --force 2>&1
        if ($LASTEXITCODE -ne 0) {
            Write-Warning "Failed to remove temporary theme. You may need to remove it manually."
        }
    } else {
        Write-Host "Theme kept in tenant gallery" -ForegroundColor Yellow
    }
}

# Example 1: Apply theme from JSON file
# .\Apply-SiteTheme.ps1 -SiteUrl "https://contoso.sharepoint.com/sites/ProjectX" -ThemeJson "@C:\themes\custom-theme.json"

# Example 2: Apply theme from inline JSON and keep it in tenant
# .\Apply-SiteTheme.ps1 -SiteUrl "https://contoso.sharepoint.com/sites/ProjectX" -ThemeJson '{"themePrimary":"#d81e05","themeLighterAlt":"#fdf5f4","themeLighter":"#f9d6d2","themeLight":"#f4b4ac","themeTertiary":"#e87060","themeSecondary":"#dd351e","themeDarkAlt":"#c31a04","themeDark":"#a51603","themeDarker":"#791002","neutralLighterAlt":"#eeeeee","neutralLighter":"#f5f5f5","neutralLight":"#e1e1e1","neutralQuaternaryAlt":"#d1d1d1","neutralQuaternary":"#c8c8c8","neutralTertiaryAlt":"#c0c0c0","neutralTertiary":"#c2c2c2","neutralSecondary":"#858585","neutralPrimaryAlt":"#4b4b4b","neutralPrimary":"#333333","neutralDark":"#272727","black":"#1d1d1d","white":"#f5f5f5"}' -KeepTheme

# Example 3: Test with WhatIf before applying
# .\Apply-SiteTheme.ps1 -SiteUrl "https://contoso.sharepoint.com/sites/ProjectX" -ThemeJson "@theme.json" -WhatIf

# Example 4: Apply with verbose output
# .\Apply-SiteTheme.ps1 -SiteUrl "https://contoso.sharepoint.com/sites/ProjectX" -ThemeJson "@theme.json" -Verbose