# Validation contracts for purpose.ncl files.
# Applied AFTER the schema contract — enforces semantic invariants beyond structural typing.
# Pattern mirrors adrs/adr-constraints.ncl: separate file, pure contracts, named exports.

let _non_empty_objectives = std.contract.custom (
  fun label =>
    fun value =>
      if std.array.length value.content_objectives == 0 then
        'Error {
          message = "purpose.ncl: content_objectives must not be empty — a purpose with no objectives is passive aspiration, not an executable intent"
        }
      else
        'Ok value
) in

let _at_least_one_hard_criterion = std.contract.custom (
  fun label =>
    fun value =>
      let hard = value.validation_criteria
        |> std.array.filter (fun vc => vc.severity == 'Hard)
      in
      if std.array.length hard == 0 then
        'Error {
          message = "purpose.ncl: at least one ValidationCriteria must have severity='Hard — a purpose with only Soft criteria has no real publication gate"
        }
      else
        'Ok value
) in

let _at_least_one_hard_seo_criterion = std.contract.custom (
  fun label =>
    fun value =>
      let hard = value.seo_criteria
        |> std.array.filter (fun sc => sc.severity == 'Hard)
      in
      if std.array.length hard == 0 then
        'Error {
          message = "purpose.ncl: at least one SeoCriterion must have severity='Hard — SEO without a hard criterion is aspirational, not enforceable"
        }
      else
        'Ok value
) in

let _objective_audience_coverage = std.contract.custom (
  fun label =>
    fun value =>
      let declared  = value.declaration.primary_audience in
      let covered   = value.content_objectives
        |> std.array.flat_map (fun obj => obj.target_audience)
      in
      let uncovered = declared
        |> std.array.filter (fun aud =>
            !(covered |> std.array.any (fun cov => cov == aud))
          )
        |> std.array.map (fun aud => std.to_string aud)
      in
      if std.array.length uncovered > 0 then
        'Error {
          message = "purpose.ncl: audiences declared in declaration.primary_audience but not covered by any ContentObjective.target_audience: %{std.string.join ", " uncovered}"
        }
      else
        'Ok value
) in

# Cross-field: every ValidationCriteria.applies_to id must reference an existing ContentObjective.id
let _valid_applies_to = std.contract.custom (
  fun label =>
    fun value =>
      let obj_ids  = value.content_objectives |> std.array.map (fun o => o.id) in
      let bad_refs = value.validation_criteria
        |> std.array.flat_map (fun vc =>
            vc.applies_to
              |> std.array.filter (fun ref_id =>
                  !(obj_ids |> std.array.any (fun oid => oid == ref_id))
                )
              |> std.array.map (fun bad_id =>
                  "criterion '%{vc.id}' applies_to unknown objective '%{bad_id}'"
                )
          )
      in
      if std.array.length bad_refs > 0 then
        std.contract.blame_with_message
          "purpose.ncl validation_criteria has invalid applies_to: %{std.string.join ", " bad_refs}"
          label
      else
        'Ok value
) in

# Cross-field: every SeoCriterion.applies_to id must reference an existing ContentObjective.id
let _seo_applies_to = std.contract.custom (
  fun label =>
    fun value =>
      let obj_ids  = value.content_objectives |> std.array.map (fun o => o.id) in
      let bad_refs = value.seo_criteria
        |> std.array.flat_map (fun sc =>
            sc.applies_to
              |> std.array.filter (fun ref_id =>
                  !(obj_ids |> std.array.any (fun oid => oid == ref_id))
                )
              |> std.array.map (fun bad_id =>
                  "seo criterion '%{sc.id}' applies_to unknown objective '%{bad_id}'"
                )
          )
      in
      if std.array.length bad_refs > 0 then
        std.contract.blame_with_message
          "purpose.ncl seo_criteria has invalid applies_to: %{std.string.join ", " bad_refs}"
          label
      else
        'Ok value
) in

{
  NonEmptyObjectives         = _non_empty_objectives,
  AtLeastOneHardCriterion    = _at_least_one_hard_criterion,
  AtLeastOneHardSeoCriterion = _at_least_one_hard_seo_criterion,
  ObjectiveAudienceCoverage  = _objective_audience_coverage,
  ValidAppliesTo             = _valid_applies_to,
  SeoAppliesTo               = _seo_applies_to,
}