param(
    [string]$Root = (Get-Location).Path,
    [string]$IndexPath,
    [Parameter(Mandatory = $true)]
    [string]$Query,
    [int]$Top = 10,
    [switch]$Json,
    [switch]$Rebuild
)

$ErrorActionPreference = "Stop"

if ([string]::IsNullOrWhiteSpace($Query)) {
    throw "Query must not be empty."
}

if (-not (Test-Path -LiteralPath $Root)) {
    throw "Root path does not exist: $Root"
}

$rootPath = (Resolve-Path -LiteralPath $Root).Path.TrimEnd([char[]]"\/")

if ([string]::IsNullOrWhiteSpace($IndexPath)) {
    $IndexPath = Join-Path (Join-Path $rootPath "_indexes") "requirements-index.json"
}

if ($Rebuild -or -not (Test-Path -LiteralPath $IndexPath)) {
    $scriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
    $buildScript = Join-Path $scriptDir "build-requirement-index.ps1"
    & $buildScript -Root $rootPath -OutputPath $IndexPath -Quiet
}

if (-not (Test-Path -LiteralPath $IndexPath)) {
    throw "Index file does not exist: $IndexPath"
}

function Get-QueryTerms {
    param([string]$Value)

    $normalized = $Value.ToLowerInvariant()
    $terms = New-Object System.Collections.Generic.List[string]

    foreach ($part in [regex]::Split($normalized, "[\s,;，；、]+")) {
        $trimmed = $part.Trim()
        if (-not [string]::IsNullOrWhiteSpace($trimmed)) {
            [void]$terms.Add($trimmed)
        }
    }

    return @($terms)
}

function Test-ContainsText {
    param(
        [string]$Haystack,
        [string]$Needle
    )

    if ([string]::IsNullOrWhiteSpace($Haystack) -or [string]::IsNullOrWhiteSpace($Needle)) {
        return $false
    }

    return $Haystack.ToLowerInvariant().Contains($Needle)
}

function Get-TextValue {
    param($Value)

    if ($null -eq $Value) {
        return ""
    }

    if ($Value -is [array]) {
        return (@($Value) -join " ")
    }

    return [string]$Value
}

function Add-Score {
    param(
        [int]$Current,
        [string]$FieldValue,
        [string]$Term,
        [int]$Weight,
        [string]$FieldName,
        [System.Collections.Generic.List[string]]$MatchedFields
    )

    if (Test-ContainsText -Haystack $FieldValue -Needle $Term) {
        [void]$MatchedFields.Add($FieldName)
        return ($Current + $Weight)
    }

    return $Current
}

$terms = @(Get-QueryTerms -Value $Query)
if ($terms.Count -eq 0) {
    throw "Query must contain at least one searchable term."
}

$rawItems = Get-Content -Raw -Encoding UTF8 -LiteralPath $IndexPath | ConvertFrom-Json
$items = @()
if ($null -ne $rawItems) {
    if ($rawItems -is [array]) {
        $items = @($rawItems)
    }
    else {
        $items = @($rawItems)
    }
}
$results = New-Object System.Collections.Generic.List[object]

foreach ($item in $items) {
    $score = 0
    $matchedTerms = New-Object System.Collections.Generic.HashSet[string]
    $matchedFields = New-Object System.Collections.Generic.List[string]

    foreach ($term in $terms) {
        $termScore = 0

        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.title) -Term $term -Weight 80 -FieldName "title" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.slug) -Term $term -Weight 60 -FieldName "slug" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.tags) -Term $term -Weight 55 -FieldName "tags" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.domain) -Term $term -Weight 35 -FieldName "domain" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.category) -Term $term -Weight 25 -FieldName "category" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.feature) -Term $term -Weight 45 -FieldName "feature" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.businessRules) -Term $term -Weight 40 -FieldName "businessRules" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.acceptance) -Term $term -Weight 25 -FieldName "acceptance" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.flow) -Term $term -Weight 18 -FieldName "flow" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.dataTables) -Term $term -Weight 12 -FieldName "dataTables" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.dictionaries) -Term $term -Weight 12 -FieldName "dictionaries" -MatchedFields $matchedFields
        $termScore = Add-Score -Current $termScore -FieldValue (Get-TextValue $item.sourceEvidence) -Term $term -Weight 8 -FieldName "sourceEvidence" -MatchedFields $matchedFields

        if ($termScore -gt 0) {
            [void]$matchedTerms.Add($term)
            $score += $termScore
        }
    }

    if ($matchedTerms.Count -eq $terms.Count) {
        $score += 30
    }

    if ($score -gt 0) {
        [void]$results.Add([pscustomobject][ordered]@{
            score = $score
            title = $item.title
            domain = $item.domain
            packageType = $item.packageType
            slug = $item.slug
            relativePath = $item.relativePath
            fullPath = $item.fullPath
            tags = @($item.tags)
            updated = $item.updated
            matchedTerms = @($matchedTerms)
            matchedFields = @($matchedFields | Select-Object -Unique)
            feature = $item.feature
            businessRules = $item.businessRules
        })
    }
}

$resultArray = @($results.ToArray())
$ranked = @($resultArray |
    Sort-Object `
        @{ Expression = "score"; Descending = $true },
        @{ Expression = "updated"; Descending = $true },
        @{ Expression = "relativePath"; Descending = $false } |
    Select-Object -First $Top)

if ($Json) {
    if ($ranked.Count -eq 0) {
        Write-Output "[]"
    }
    elseif ($ranked.Count -eq 1) {
        Write-Output "[$($ranked[0] | ConvertTo-Json -Depth 8)]"
    }
    else {
        ConvertTo-Json -InputObject $ranked -Depth 8
    }
    return
}

if ($ranked.Count -eq 0) {
    Write-Host "No matching requirement packages found."
    return
}

foreach ($result in $ranked) {
    Write-Host "[$($result.score)] $($result.title) ($($result.domain)/$($result.slug))"
    Write-Host "  path: $($result.relativePath)"
    if ($result.tags.Count -gt 0) {
        Write-Host "  tags: $(@($result.tags) -join ', ')"
    }
    Write-Host "  matched: $(@($result.matchedTerms) -join ', ') in $(@($result.matchedFields) -join ', ')"
    if (-not [string]::IsNullOrWhiteSpace($result.feature)) {
        Write-Host "  feature: $($result.feature)"
    }
    Write-Host ""
}