using System.Text.Json.Nodes;
using System.Text.RegularExpressions;
using w4c_workflows.Models;
using w4c_workflows.Models.Nodes;
using w4c_workflows.Services.Security;

namespace w4c_workflows.Services.Nodes;

// Validation half of the node-graph compiler: per-step id/blueprint/parameter
// and credential-alias checks. Compilation flow and edge handling live in
// NodeGraphCompiler.cs / NodeGraphCompiler.Edges.cs.

public sealed partial class NodeGraphCompiler
{
    // ------------------------------------------------------------------ steps

    /// <summary>
    /// Validates each step's credential aliases: they must be declared by the
    /// blueprint, required links must be present, and an alias must not be bound
    /// to two different credentials within one workflow (which is what lets the
    /// run resolve credentials once into a single alias → data map).
    /// </summary>
    private static void ValidateCredentialAliases(
        IReadOnlyList<NodeGraphNode> nodes,
        IReadOnlyDictionary<string, NodeBlueprint> blueprints,
        List<string> errors)
    {
        var seen = new Dictionary<string, string>(StringComparer.Ordinal);

        foreach (var node in nodes)
        {
            var blueprint = blueprints[node.Id];
            var declared = blueprint.Credentials.Select(c => c.Alias).ToHashSet(StringComparer.Ordinal);

            foreach (var (alias, reference) in node.CredentialRefs)
            {
                if (!declared.Contains(alias))
                    errors.Add($"task '{node.Id}': node '{blueprint.Type}' has no credential alias '{alias}'");

                if (seen.TryGetValue(alias, out var existing) && !string.Equals(existing, reference, StringComparison.Ordinal))
                    errors.Add($"credential alias '{alias}' is bound to two different credentials ('{existing}' and '{reference}')");
                else
                    seen[alias] = reference;
            }

            foreach (var link in blueprint.Credentials.Where(c => c.Required))
            {
                if (!node.CredentialRefs.ContainsKey(link.Alias))
                    errors.Add($"task '{node.Id}': node '{blueprint.Type}' requires credential '{link.Alias}'");
            }
        }
    }

    private bool ValidateStep(TaskDefinition task, string label, List<string> errors)
    {
        if (string.IsNullOrWhiteSpace(task.Id))
        {
            errors.Add($"{label}.id is required");
            return false;
        }
        if (string.Equals(task.Id, "root", StringComparison.OrdinalIgnoreCase))
        {
            errors.Add($"{label}.id 'root' is reserved");
            return false;
        }
        if (!StepIdRegex().IsMatch(task.Id) || task.Id.Length > 100)
        {
            errors.Add($"{label}.id '{task.Id}' is invalid");
            return false;
        }

        if (task.Node == null)
        {
            errors.Add($"task '{task.Id}': a node workflow step must declare 'node'");
            return false;
        }
        if (string.IsNullOrWhiteSpace(task.Node.Type))
        {
            errors.Add($"task '{task.Id}'.node.type is required");
            return false;
        }
        if (task.Entry != null || !string.IsNullOrWhiteSpace(task.Language))
        {
            errors.Add($"task '{task.Id}': 'node' and 'entry'/'language' are mutually exclusive");
            return false;
        }

        return true;
    }

    private NodeBlueprint? ResolveBlueprint(TaskDefinition task, List<string> errors)
    {
        var version = task.Node!.Version;
        var blueprint = _catalog.Resolve(task.Node.Type!, version);
        if (blueprint != null)
            return blueprint;

        errors.Add(version is null or 0
            ? $"task '{task.Id}': unknown node type '{task.Node.Type}'"
            : $"task '{task.Id}': node type '{task.Node.Type}' has no version {version}");
        return null;
    }

    private static NodeGraphNode BuildNode(TaskDefinition task, NodeBlueprint blueprint, List<string> errors)
    {
        var parameters = NodeParameterReader.ToJsonObject(task.Parameters);
        ValidateParameters(task.Id!, blueprint, parameters, errors);

        if (!string.IsNullOrWhiteSpace(task.RunMode) && !RunModes.Contains(task.RunMode))
        {
            errors.Add(
                $"task '{task.Id}'.runMode '{task.RunMode}' is invalid: expected one of {string.Join(", ", RunModes)}");
        }

        return new NodeGraphNode
        {
            Id = task.Id!,
            Blueprint = blueprint,
            Parameters = parameters,
            CredentialRefs = task.Credentials != null
                ? new Dictionary<string, string>(task.Credentials, StringComparer.Ordinal)
                : new Dictionary<string, string>(),
            RunMode = task.RunMode,
            ContinueOnFail = task.ContinueOnFail ?? false,
            Retry = task.Retry,
        };
    }

    private static void ValidateParameters(
        string taskId, NodeBlueprint blueprint, JsonObject parameters, List<string> errors)
    {
        foreach (var (name, value) in parameters)
        {
            if (!blueprint.HasParameter(name))
            {
                errors.Add($"task '{taskId}': node '{blueprint.Type}' has no parameter '{name}'");
                continue;
            }

            var descriptor = blueprint.FindParameter(name);
            if (descriptor != null)
                ValidateParameterValue(taskId, descriptor, value, errors);
        }

        foreach (var descriptor in blueprint.Parameters.Where(p => p.Required))
        {
            if (!parameters.ContainsKey(descriptor.Name))
                errors.Add($"task '{taskId}': node '{blueprint.Type}' requires parameter '{descriptor.Name}'");
        }
    }

    private static void ValidateParameterValue(
        string taskId, NodeParameter descriptor, JsonNode? value, List<string> errors)
    {
        // Expressions are resolved at run time, so their static type is unknown.
        if (IsExpression(value))
            return;

        switch (descriptor.Type)
        {
            case NodeParameterType.Options:
            case NodeParameterType.MultiOptions:
                ValidateOptionValue(taskId, descriptor, value, errors);
                break;
            case NodeParameterType.Boolean when value is not null && !IsBoolean(value):
                errors.Add($"task '{taskId}': parameter '{descriptor.Name}' must be a boolean");
                break;
            case NodeParameterType.Number when value is not null && !IsNumber(value):
                errors.Add($"task '{taskId}': parameter '{descriptor.Name}' must be a number");
                break;
        }
    }

    private static bool IsExpression(JsonNode? value)
        => value is JsonValue jsonValue &&
           jsonValue.TryGetValue<string>(out var text) &&
           (text.StartsWith('=') || text.Contains("{{", StringComparison.Ordinal));

    private static void ValidateOptionValue(
        string taskId, NodeParameter descriptor, JsonNode? value, List<string> errors)
    {
        if (value is null || descriptor.Options is not { Count: > 0 })
            return;

        var allowed = descriptor.Options.Select(option => option.Value.GetRawText()).ToHashSet(StringComparer.Ordinal);

        if (descriptor.Type == NodeParameterType.MultiOptions && value is JsonArray array)
        {
            foreach (var element in array)
            {
                if (element is not null && !allowed.Contains(element.ToJsonString()))
                    errors.Add($"task '{taskId}': parameter '{descriptor.Name}' has unsupported value {element.ToJsonString()}");
            }
            return;
        }

        if (!allowed.Contains(value.ToJsonString()))
            errors.Add($"task '{taskId}': parameter '{descriptor.Name}' has unsupported value {value.ToJsonString()}");
    }

    private static bool IsBoolean(JsonNode value)
        => value is JsonValue jsonValue && jsonValue.TryGetValue<bool>(out _);

    private static bool IsNumber(JsonNode value)
        => value is JsonValue jsonValue &&
           (jsonValue.TryGetValue<decimal>(out _) || jsonValue.TryGetValue<double>(out _) || jsonValue.TryGetValue<long>(out _));
}