## Property-Based Tests for Conflict Minimality
##
## This module tests the property that minimal conflict extraction
## produces the smallest possible set of conflicting incompatibilities.
##
## Property: Conflict Minimality
## For any set of incompatibilities that cause a conflict,
## the extracted minimal set should be a subset of the original set,
## and removing any incompatibility from the minimal set should
## result in a non-conflicting set (or at least a smaller conflict).
##
## Requirements:
## - 7.5: Provide minimal conflicting requirements

import std/[unittest, random, sequtils, options, algorithm]
import ../src/nip/resolver/conflict_detection
import ../src/nip/resolver/solver_types
import ../src/nip/manifest_parser

suite "Conflict Minimality Properties":
  
  test "Property: Minimal conflict is subset of original":
    ## For any set of incompatibilities, the minimal conflict
    ## should be a subset of the original set.
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    # Generate random incompatibilities
    var incompatibilities: seq[Incompatibility] = @[]
    
    for i in 0 ..< 10:
      incompatibilities.add(Incompatibility(
        terms: @[],
        cause: if i mod 3 == 0: Root elif i mod 3 == 1: Dependency else: IncompatibilityCause.VariantConflict,
        externalContext: "Incomp " & $i,
        fromPackage: some("pkg" & $i),
        fromVersion: none(SemanticVersion)
      ))
    
    let minimal = extractMinimalConflict(incompatibilities)
    
    check minimal.isSome
    
    # The minimal set should be a subset of the original
    let minimalSet = minimal.get()
    check minimalSet.len <= incompatibilities.len
    
    # Every incompatibility in minimal should be in original
    for minIncomp in minimalSet:
      let found = incompatibilities.anyIt(
        it.externalContext == minIncomp.externalContext and
        it.cause == minIncomp.cause
      )
      check found
  
  test "Property: Minimal conflict preserves root incompatibilities":
    ## Root incompatibilities (user requirements) should always
    ## be preserved in the minimal conflict set.
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    # Create a mix of incompatibilities with at least one root
    let rootIncomp = Incompatibility(
      terms: @[],
      cause: Root,
      externalContext: "User requirement",
      fromPackage: some("nginx"),
      fromVersion: none(SemanticVersion)
    )
    
    var incompatibilities = @[rootIncomp]
    
    for i in 0 ..< 5:
      incompatibilities.add(Incompatibility(
        terms: @[],
        cause: Dependency,
        externalContext: "Dependency " & $i,
        fromPackage: some("pkg" & $i),
        fromVersion: none(SemanticVersion)
      ))
    
    let minimal = extractMinimalConflict(incompatibilities)
    
    check minimal.isSome
    
    # Root incompatibilities should be preserved
    let hasRoot = minimal.get().anyIt(it.cause == Root)
    check hasRoot
  
  test "Property: Minimal conflict is deterministic":
    ## Extracting minimal conflict from the same set should
    ## always produce the same result.
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    let incompatibilities = @[
      Incompatibility(
        terms: @[],
        cause: Root,
        externalContext: "Root",
        fromPackage: some("pkg1"),
        fromVersion: none(SemanticVersion)
      ),
      Incompatibility(
        terms: @[],
        cause: Dependency,
        externalContext: "Dep1",
        fromPackage: some("pkg2"),
        fromVersion: none(SemanticVersion)
      ),
      Incompatibility(
        terms: @[],
        cause: Dependency,
        externalContext: "Dep2",
        fromPackage: some("pkg3"),
        fromVersion: none(SemanticVersion)
      )
    ]
    
    # Extract minimal conflict multiple times
    let minimal1 = extractMinimalConflict(incompatibilities)
    let minimal2 = extractMinimalConflict(incompatibilities)
    let minimal3 = extractMinimalConflict(incompatibilities)
    
    # All results should be the same
    check minimal1.isSome
    check minimal2.isSome
    check minimal3.isSome
    
    check minimal1.get().len == minimal2.get().len
    check minimal2.get().len == minimal3.get().len
    
    # The contexts should match
    let contexts1 = minimal1.get().mapIt(it.externalContext).sorted()
    let contexts2 = minimal2.get().mapIt(it.externalContext).sorted()
    let contexts3 = minimal3.get().mapIt(it.externalContext).sorted()
    
    check contexts1 == contexts2
    check contexts2 == contexts3
  
  test "Property: Minimal conflict handles empty input":
    ## Extracting minimal conflict from empty set should return None.
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    let minimal = extractMinimalConflict(@[])
    
    check minimal.isNone
  
  test "Property: Minimal conflict handles single incompatibility":
    ## Extracting minimal conflict from single incompatibility
    ## should return that incompatibility.
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    let incomp = Incompatibility(
      terms: @[],
      cause: Root,
      externalContext: "Single",
      fromPackage: some("pkg"),
      fromVersion: none(SemanticVersion)
    )
    
    let minimal = extractMinimalConflict(@[incomp])
    
    check minimal.isSome
    check minimal.get().len == 1
    check minimal.get()[0].externalContext == "Single"
  
  test "Property: Minimal conflict reduces redundancy":
    ## The minimal conflict should have fewer or equal incompatibilities
    ## than the original set (it should not add incompatibilities).
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    # Create a large set of incompatibilities
    var incompatibilities: seq[Incompatibility] = @[]
    
    for i in 0 ..< 20:
      incompatibilities.add(Incompatibility(
        terms: @[],
        cause: if i == 0: Root else: Dependency,
        externalContext: "Incomp " & $i,
        fromPackage: some("pkg" & $(i mod 5)),
        fromVersion: none(SemanticVersion)
      ))
    
    let minimal = extractMinimalConflict(incompatibilities)
    
    check minimal.isSome
    
    # Minimal should not have more incompatibilities than original
    check minimal.get().len <= incompatibilities.len
    
    # Minimal should have at least 1 incompatibility (if original had any)
    check minimal.get().len >= 1
  
  test "Property: Minimal conflict preserves conflict causes":
    ## The minimal conflict should preserve the causes of conflicts
    ## (Root, Dependency, VariantConflict, etc.)
    ##
    ## **Feature: nip-dependency-resolution, Property 6: Conflict Minimality**
    ## **Validates: Requirements 7.5**
    
    let incompatibilities = @[
      Incompatibility(
        terms: @[],
        cause: Root,
        externalContext: "Root",
        fromPackage: some("pkg1"),
        fromVersion: none(SemanticVersion)
      ),
      Incompatibility(
        terms: @[],
        cause: Dependency,
        externalContext: "Dep",
        fromPackage: some("pkg2"),
        fromVersion: none(SemanticVersion)
      ),
      Incompatibility(
        terms: @[],
        cause: IncompatibilityCause.VariantConflict,
        externalContext: "Variant",
        fromPackage: some("pkg3"),
        fromVersion: none(SemanticVersion)
      )
    ]
    
    let minimal = extractMinimalConflict(incompatibilities)
    
    check minimal.isSome
    
    # The minimal set should contain at least one of each cause type
    # (or at least preserve the causes that are present)
    let causes = minimal.get().mapIt(it.cause)
    
    # Should have at least one incompatibility
    check causes.len >= 1
    
    # All causes in minimal should be in original
    for cause in causes:
      let found = incompatibilities.anyIt(it.cause == cause)
      check found