# =========================================================================
# Shared Mock VCF Text File Generator
# =========================================================================
write_mock_vcf <- function(include_ad = TRUE, missing_gt = FALSE) {
  
  # Cleanly determine the conditional lines first
  ad_header <- if (include_ad) "##FORMAT=<ID=AD,Number=R,Type=Integer,Description=\"Allele Depth\">" else ""
  format_field <- if (include_ad) "GT:AD" else "GT"
  
  vcf_lines <- c(
    "##fileformat=VCFv4.2",
    "##FORMAT=<ID=GT,Number=1,Type=String,Description=\"Genotype\">",
    ad_header,
    paste0("#CHROM\tPOS\tID\tREF\tALT\tQUAL\tFILTER\tINFO\tFORMAT\tInd1\tInd2\tInd3"),
    
    # Chromosome 1 - Variant 1 (Clean)
    paste0("Chr1\t1001\trs1\tA\tG\t100\tPASS\t.\t", 
           format_field, "\t0/1", 
           if (include_ad) ":10,10" else "", "\t0/0", 
           if (include_ad) ":20,0" else "", "\t1/1", 
           if (include_ad) ":0,20" else ""),
    
    # Chromosome 1 - Variant 2 (Injected Missing Data conditional)
    paste0("Chr1\t2002\trs2\tC\tT\t100\tPASS\t.\t", 
           format_field, "\t", 
           if (missing_gt) "./.:0,0" else if (include_ad) "0/1:12,8" else "0/1", "\t0/1", 
           if (include_ad) ":10,10" else "", "\t0/0", 
           if (include_ad) ":20,0" else ""),
    
    # Chromosome 2 - Variant 3 (Single marker on a chromosome to check for NaN bug)
    paste0("Chr2\t5005\trs3\tT\tG\t100\tPASS\t.\t", 
           format_field, "\t1/1", 
           if (include_ad) ":0,20" else "", "\t0/1", 
           if (include_ad) ":11,9" else "", "\t0/0", 
           if (include_ad) ":20,0" else "")
  )
  
  # Clean out any empty strings remaining from the 'else' branches
  vcf_lines <- vcf_lines[vcf_lines != ""]
  
  tmp_file <- tempfile(fileext = ".vcf")
  writeLines(vcf_lines, tmp_file)
  return(tmp_file)
}

# =========================================================================
# 1. Structural Sanity Parsing (Standard GT Ingestion)
# =========================================================================
test_that("ReadVCF correctly extracts and builds genetic proxy footprints from GT matrices", {
  vcf_path <- write_mock_vcf(include_ad = FALSE)
  on.exit(unlink(vcf_path)) # Guaranteed file destruction cleanup
  
  res <- ReadVCF(File = vcf_path, AlleleDepthField = NULL, MaxMarkerMissing = 1.0, 
                 MaxIndMissing = 1.0, Verbose = FALSE)
  
  # Structural Outputs Assertions
  expect_type(res, "list")
  expect_named(res, c("Geno", "MarkerInfo", "GeneticMap"))
  
  # Dimension mapping validation (3 individuals, 3 variants)
  expect_length(res$Geno, 3)
  expect_equal(nrow(res$MarkerInfo), 3)
  expect_equal(dim(res$GeneticMap), c(3, 3))
  
  # String synthesis verification block
  expect_equal(res$MarkerInfo$MARKER[1], "Chr1_1001")
  expect_equal(colnames(res$GeneticMap), c("Chromosome", "Marker", "Distance"))
})

# =========================================================================
# 2. Field String Extraction (Optional Depth Allocations)
# =========================================================================
test_that("ReadVCF switches dynamically to Allele Depth Field configurations", {
  vcf_path <- write_mock_vcf(include_ad = TRUE)
  on.exit(unlink(vcf_path))
  
  # Inject mock formats handler for .FormatVariant hook tracing
  expect_error(
    ReadVCF(File = vcf_path, AlleleDepthField = "AD", AlleleDepthType = "alleles", Verbose = FALSE),
    NA
  )
  
  # Verify that missing type mappings trigger checks
  expect_error(
    ReadVCF(File = vcf_path, AlleleDepthField = "AD", AlleleDepthType = "invalid_type", Verbose = FALSE),
    regexp = "chosen among|informed along with"
  )
})
  
# =========================================================================
# 3. Missing Value Filtering Logic Branches
# =========================================================================
test_that("Missing value filters appropriately drop elements and update metadata", {
  # Build a file where variant 2 has explicit missing markers
  vcf_path <- write_mock_vcf(include_ad = TRUE, missing_gt = TRUE)
  on.exit(unlink(vcf_path))
  
  # Run clean pass (MaxMarkerMissing = 1.0 means no drops)
  res_clean <- ReadVCF(File = vcf_path, MaxMarkerMissing = 1.0, MaxIndMissing = 1.0, Verbose = FALSE)
  expect_length(res_clean$Geno, 3)
  
  # Run strict missing pass (Variant 2 has 1/3 = 33% missingness, should drop at 20% limit)
  res_filtered <- ReadVCF(File = vcf_path, MaxMarkerMissing = 0.20, MaxIndMissing = 1.0, Verbose = FALSE)
  
  # Geno list and MarkerInfo arrays must shrink down simultaneously
  expect_length(res_filtered$Geno, 2)
  expect_equal(nrow(res_filtered$MarkerInfo), 2)
  expect_false("Chr1_2002" %in% names(res_filtered$Geno))
})

# =========================================================================
# 4. Physical Map Proxy Boundary Protections (Preventing NaN)
# =========================================================================
test_that("Genetic map distance calculations wrap cleanly across boundaries without generating NaN", {
  vcf_path <- write_mock_vcf(include_ad = FALSE)
  on.exit(unlink(vcf_path))
  
  res <- ReadVCF(File = vcf_path, MaxMarkerMissing = 1.0, MaxIndMissing = 1.0, Verbose = FALSE)
  
  # Verify bounded distance assignments (Chr1 Min marker should always resolve to 0)
  expect_equal(res$GeneticMap$Distance[res$GeneticMap$Marker == "Chr1_1001"], 0)
  expect_equal(res$GeneticMap$Distance[res$GeneticMap$Marker == "Chr1_2002"], 100)
  
  # Check single marker chromosome handling (The safety bug check)
  chr2_dist <- res$GeneticMap$Distance[res$GeneticMap$Marker == "Chr2_5005"]
  expect_false(is.nan(chr2_dist))
  expect_equal(chr2_dist, 0)
})

# =========================================================================
# 5. Missing File Safeguards & Terminal Mutes
# =========================================================================
test_that("ReadVCF protects file systems and maintains mute constraints cleanly", {
  expect_error(ReadVCF(File = "non_existent_file.vcf", Verbose = FALSE), regexp = "No file was found")
  
  vcf_path <- write_mock_vcf(include_ad = FALSE)
  on.exit(unlink(vcf_path))
  
  expect_silent(ReadVCF(File = vcf_path, Verbose = FALSE))
})