// SPDX-License-Identifier: BUSL-1.1
// Copyright (c) 2025 StellaOps
// Sprint: SPRINT_20260122_039_Scanner_runtime_linkage_verification
// Task: RLV-001 - Define function_map Predicate Schema

using System.Text.Json.Serialization;

namespace StellaOps.Scanner.Reachability.FunctionMap;

/// <summary>
/// Function map predicate that declares expected call-paths for a service.
/// Used for runtime→static linkage verification via eBPF observation.
///
/// This predicate serves as the "contract" that runtime observations will be verified against.
/// It is typically generated from SBOM + static analysis and signed for attestation.
/// </summary>
/// <remarks>
/// Predicate type: https://stella.ops/predicates/function-map/v1
///
/// Key concepts:
/// - Uses nodeHash recipe from witness-v1 for consistency (PURL + normalized symbol)
/// - expectedPaths defines call-paths from entrypoints to "hot functions"
/// - probeTypes specifies acceptable eBPF probe types for each function
/// - coverage.minObservationRate maps to "≥ 95% of calls witnessed" requirement
/// - optional flag handles conditional paths (feature flags, error handlers)
/// </remarks>
public sealed record FunctionMapPredicate
{
    /// <summary>
    /// Predicate type URI.
    /// </summary>
    [JsonPropertyName("_type")]
    public string Type { get; init; } = FunctionMapSchema.PredicateType;

    /// <summary>
    /// Subject artifact that this function map applies to.
    /// </summary>
    [JsonPropertyName("subject")]
    public required FunctionMapSubject Subject { get; init; }

    /// <summary>
    /// The predicate payload containing the function map definition.
    /// </summary>
    [JsonPropertyName("predicate")]
    public required FunctionMapPredicatePayload Predicate { get; init; }
}

/// <summary>
/// Subject artifact for the function map.
/// </summary>
public sealed record FunctionMapSubject
{
    /// <summary>
    /// Package URL of the subject artifact.
    /// Example: "pkg:oci/myservice@sha256:abc123..."
    /// </summary>
    [JsonPropertyName("purl")]
    public required string Purl { get; init; }

    /// <summary>
    /// Digest(s) of the subject artifact.
    /// Key is algorithm (sha256, sha512), value is hex-encoded hash.
    /// </summary>
    [JsonPropertyName("digest")]
    public required IReadOnlyDictionary<string, string> Digest { get; init; }

    /// <summary>
    /// Optional artifact name.
    /// </summary>
    [JsonPropertyName("name")]
    public string? Name { get; init; }
}

/// <summary>
/// The main predicate payload containing function map definition.
/// </summary>
public sealed record FunctionMapPredicatePayload
{
    /// <summary>
    /// Schema version of this predicate.
    /// </summary>
    [JsonPropertyName("schemaVersion")]
    public string SchemaVersion { get; init; } = FunctionMapSchema.SchemaVersion;

    /// <summary>
    /// Service name that this function map applies to.
    /// </summary>
    [JsonPropertyName("service")]
    public required string Service { get; init; }

    /// <summary>
    /// Build ID or version of the service.
    /// Used to correlate with specific builds.
    /// </summary>
    [JsonPropertyName("buildId")]
    public string? BuildId { get; init; }

    /// <summary>
    /// References to source materials used to generate this function map.
    /// </summary>
    [JsonPropertyName("generatedFrom")]
    public FunctionMapGeneratedFrom? GeneratedFrom { get; init; }

    /// <summary>
    /// Expected call-paths that should be observed at runtime.
    /// </summary>
    [JsonPropertyName("expectedPaths")]
    public required IReadOnlyList<ExpectedPath> ExpectedPaths { get; init; }

    /// <summary>
    /// Coverage thresholds for verification.
    /// </summary>
    [JsonPropertyName("coverage")]
    public required CoverageThresholds Coverage { get; init; }

    /// <summary>
    /// When this function map was generated.
    /// </summary>
    [JsonPropertyName("generatedAt")]
    public required DateTimeOffset GeneratedAt { get; init; }

    /// <summary>
    /// Optional generator tool information.
    /// </summary>
    [JsonPropertyName("generator")]
    public GeneratorInfo? Generator { get; init; }

    /// <summary>
    /// Optional metadata for extensions.
    /// </summary>
    [JsonPropertyName("metadata")]
    public IReadOnlyDictionary<string, object>? Metadata { get; init; }
}

/// <summary>
/// References to source materials used to generate the function map.
/// </summary>
public sealed record FunctionMapGeneratedFrom
{
    /// <summary>
    /// SHA256 digest of the SBOM used.
    /// </summary>
    [JsonPropertyName("sbomRef")]
    public string? SbomRef { get; init; }

    /// <summary>
    /// SHA256 digest of the static analysis results used.
    /// </summary>
    [JsonPropertyName("staticAnalysisRef")]
    public string? StaticAnalysisRef { get; init; }

    /// <summary>
    /// SHA256 digest of the binary analysis results used.
    /// </summary>
    [JsonPropertyName("binaryAnalysisRef")]
    public string? BinaryAnalysisRef { get; init; }

    /// <summary>
    /// Hot function patterns used for filtering.
    /// </summary>
    [JsonPropertyName("hotFunctionPatterns")]
    public IReadOnlyList<string>? HotFunctionPatterns { get; init; }
}

/// <summary>
/// Coverage thresholds for function map verification.
/// </summary>
public sealed record CoverageThresholds
{
    /// <summary>
    /// Minimum observation rate required for verification to pass.
    /// Value between 0.0 and 1.0 (e.g., 0.95 = 95% of expected calls must be observed).
    /// </summary>
    [JsonPropertyName("minObservationRate")]
    public double MinObservationRate { get; init; } = FunctionMapSchema.DefaultMinObservationRate;

    /// <summary>
    /// Observation window in seconds.
    /// Only observations within this window are considered for verification.
    /// </summary>
    [JsonPropertyName("windowSeconds")]
    public int WindowSeconds { get; init; } = FunctionMapSchema.DefaultWindowSeconds;

    /// <summary>
    /// Minimum number of observations required before verification can succeed.
    /// Prevents false positives from low traffic periods.
    /// </summary>
    [JsonPropertyName("minObservationCount")]
    public int? MinObservationCount { get; init; }

    /// <summary>
    /// Whether to fail on unexpected symbols (not in the function map).
    /// When false (default), unexpected symbols are reported but don't fail verification.
    /// </summary>
    [JsonPropertyName("failOnUnexpected")]
    public bool FailOnUnexpected { get; init; }
}

/// <summary>
/// Information about the tool that generated this function map.
/// </summary>
public sealed record GeneratorInfo
{
    /// <summary>
    /// Name of the generator tool.
    /// </summary>
    [JsonPropertyName("name")]
    public string? Name { get; init; }

    /// <summary>
    /// Version of the generator tool.
    /// </summary>
    [JsonPropertyName("version")]
    public string? Version { get; init; }

    /// <summary>
    /// Optional commit hash of the generator tool.
    /// </summary>
    [JsonPropertyName("commit")]
    public string? Commit { get; init; }
}