# The .txt twins are generated, and this is what makes that true.
#
#   Invoke-Pester .\tests
#
# scripts/plaintext_twins.py has always shipped a --check mode, and its
# docstring claimed "the test suite runs --check". Nothing ran it. So README.txt
# could drift from README.md silently, and CHANGELOG.txt - which no generator
# covered at all - actually did.
#
# A twin that disagrees with the file it mirrors is worse than no twin: it is a
# second document that looks authoritative and is wrong.

# -Skip is evaluated during DISCOVERY, before BeforeAll runs, so a python
# lookup done in BeforeAll leaves the flag $null and the real check silently
# skips - which is how this test first "passed" while verifying nothing.
BeforeDiscovery {
    $script:Python = $null
    foreach ($candidate in @('python', 'python3', 'py')) {
        $cmd = Get-Command $candidate -ErrorAction SilentlyContinue
        if ($cmd) { $script:Python = $cmd.Source; break }
    }
}

BeforeAll {
    $script:RepoRoot = Split-Path -Parent $PSScriptRoot
    $script:Generator = Join-Path $script:RepoRoot "scripts\plaintext_twins.py"

    $script:Python = $null
    foreach ($candidate in @('python', 'python3', 'py')) {
        $cmd = Get-Command $candidate -ErrorAction SilentlyContinue
        if ($cmd) { $script:Python = $cmd.Source; break }
    }
}

Describe "plain-text twins" {

    It "the generator is where the tests and the docs say it is" {
        Test-Path -LiteralPath $script:Generator | Should -BeTrue
    }

    It "every .md that owes a twin has one" {
        $pairs = Select-String -Path $script:Generator -Pattern '^\s*\("([^"]+\.md)",\s*"([^"]+\.txt)"\),' |
            ForEach-Object { [pscustomobject]@{ Md = $_.Matches[0].Groups[1].Value; Txt = $_.Matches[0].Groups[2].Value } }

        $pairs.Count | Should -BeGreaterThan 0 -Because "PAIRS in plaintext_twins.py is what this suite checks"
        foreach ($p in $pairs) {
            Test-Path -LiteralPath (Join-Path $script:RepoRoot $p.Md) | Should -BeTrue -Because "$($p.Md) is listed in PAIRS"
            Test-Path -LiteralPath (Join-Path $script:RepoRoot $p.Txt) | Should -BeTrue -Because "$($p.Md) owes a twin at $($p.Txt)"
        }
    }

    It "every twin is in sync with its markdown" -Skip:(-not $script:Python) {
        Push-Location $script:RepoRoot
        try {
            $output = & $script:Python $script:Generator --check 2>&1
            $code = $LASTEXITCODE
        }
        finally { Pop-Location }

        $code | Should -Be 0 -Because ($output -join "`n")
    }

    It "reports the python that was missing rather than passing quietly" -Skip:([bool]$script:Python) {
        # Not a pass. If this is the test you are reading, --check never ran:
        # install python, or regenerate the twins by hand before shipping.
        Set-ItResult -Inconclusive -Because "no python on PATH, so the twins were not verified"
    }
}