#Requires -Modules @{ ModuleName = 'Pester'; ModuleVersion = '5.0.0' }

<#
    The write gate has exactly one origin: ShouldProcess.

    The tests that matter here are the negative ones. -Debug and -Verbose are the two
    switches an operator is most likely to reach for believing they make a run safe,
    and neither does. If that ever changes silently, someone will run an enforcing
    pass believing they are looking rather than touching.
#>

BeforeAll {
    $repoRoot = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
    . (Join-Path $repoRoot 'tests/TestHelpers.ps1')
    foreach ($file in (Get-PersonaSourceFile -RepoRoot $repoRoot)) { . $file }

    $script:target = 'extension_<EXTENSION-APP-ID>_<PERSONA>'
    $script:config = New-TestRuntimeConfiguration -TargetAttribute $target
    $script:population = @(New-TestPopulation -Count 12 -TargetAttribute $target)

    $script:entryScript = Join-Path $repoRoot 'Invoke-PersonaEngine.ps1'
}

Describe 'Mode derives from the gate alone' -Tag 'Safety' {

    BeforeEach {
        Mock Get-PersonaUsers { $script:population }
        Mock Write-Host { }
        # Two of these tests raise the verbose and debug preferences deliberately.
        # Without this the per-user diagnostic lines flood the whole suite's output.
        Mock Write-Verbose { }
        Mock Set-UserPersonaAttribute { [pscustomobject]@{ Succeeded = $true } }
    }

    It 'writes when -Debug is active and the gate allows it' {
        # -Debug must not imply read-only. An operator who believed otherwise would
        # reach for it as a safety control and get an enforcing run.
        $DebugPreference = 'Continue'

        $outcome = Invoke-PersonaEngineRun -Configuration $config -TargetAttribute $target `
            -Context (New-TestAuditContext -Mode 'Enforce') `
            -IsEnforcing -Tracing `
            -ShouldProcessGate { param($t, $d) $true }

        $outcome.Counters.Updated | Should -BeGreaterThan 0
        Should -Invoke Set-UserPersonaAttribute -Times $outcome.Counters.Updated -Exactly
    }

    It 'writes when -Verbose is active and the gate allows it' {
        $VerbosePreference = 'Continue'

        $outcome = Invoke-PersonaEngineRun -Configuration $config -TargetAttribute $target `
            -Context (New-TestAuditContext -Mode 'Enforce') `
            -IsEnforcing `
            -ShouldProcessGate { param($t, $d) $true }

        $outcome.Counters.Updated | Should -BeGreaterThan 0
    }

    It 'refuses every write when the gate refuses, regardless of IsEnforcing' {
        # IsEnforcing shapes the Action label; the gate decides the write. A
        # disagreement between them must resolve in favour of not writing.
        $outcome = Invoke-PersonaEngineRun -Configuration $config -TargetAttribute $target `
            -Context (New-TestAuditContext -Mode 'Enforce') `
            -IsEnforcing `
            -ShouldProcessGate { param($t, $d) $false }

        Should -Invoke Set-UserPersonaAttribute -Times 0 -Exactly
        $outcome.Counters.Updated | Should -Be 0
        $outcome.Counters.WouldUpdate | Should -BeGreaterThan 0
    }

    It 'honours a gate that allows some accounts and refuses others' {
        # A per-account gate, as ShouldProcess is when the operator answers "Yes"
        # rather than "Yes to All". Both buckets must be populated in one run.
        $script:gateCalls = 0

        $outcome = Invoke-PersonaEngineRun -Configuration $config -TargetAttribute $target `
            -Context (New-TestAuditContext -Mode 'Enforce') `
            -IsEnforcing `
            -ShouldProcessGate { param($t, $d) ($script:gateCalls++ % 2) -eq 0 }

        ($outcome.Counters.Updated + $outcome.Counters.WouldUpdate) | Should -BeGreaterThan 0
        $outcome.Counters.Updated | Should -BeGreaterThan 0
        $outcome.Counters.WouldUpdate | Should -BeGreaterThan 0
    }
}

Describe 'The entry script declares the safety contract it promises' -Tag 'Safety' {

    BeforeAll {
        $script:entryText = Get-Content -LiteralPath $script:entryScript -Raw
    }

    It 'declares SupportsShouldProcess with a High confirm impact' {
        $entryText | Should -Match 'SupportsShouldProcess\s*=\s*\$true'
        $entryText | Should -Match "ConfirmImpact\s*=\s*'High'"
    }

    It 'does not declare a preview or no-write parameter of its own' {
        # Two sources of truth for the write gate is the defect class Principle III
        # exists to prevent. -WhatIf is the only approved control.
        $entryText | Should -Not -Match '\[switch\]\s*\$Preview'
        $entryText | Should -Not -Match '\[switch\]\s*\$NoWrite'
        $entryText | Should -Not -Match '\[switch\]\s*\$ReadOnly'
        $entryText | Should -Not -Match '\[switch\]\s*\$DryRun'
    }

    It 'derives the mode from ShouldProcess' {
        $entryText | Should -Match '\$PSCmdlet\.ShouldProcess\('
    }

    It 'does not derive the mode from DebugPreference or WhatIfPreference' {
        # Reading the preference variables directly would reintroduce a second source
        # of truth by the back door.
        $entryText | Should -Not -Match '\$WhatIfPreference'
        $entryText | Should -Not -Match 'if\s*\(\s*\$DebugPreference'
    }
}