using System.Net.Http.Headers;
using System.Text;
using System.Text.Json.Nodes;
using w4c_workflows.Models.Credentials;
using w4c_workflows.Models.Nodes;
using w4c_workflows.Services.Credentials;
using w4c_workflows.Services.Nodes.Binary;
using w4c_workflows.Services.Security;

namespace w4c_workflows.Services.Nodes.Executors;

// Request-shaping half of the HTTP Request node: static/pagination headers and
// the JSON/form/raw/multipart/binary body builders.

public sealed partial class HttpRequestNodeExecutor
{
    // ------------------------------------------------------------------ request

    private static void ApplyHeaders(
        NodeExecutionContext context,
        HttpRequestMessage request,
        IReadOnlyDictionary<string, string> overrides)
    {
        if (NodeValueAccess.ReadBool(context.Parameters, "sendHeaders") && context.Parameters["headers"] is JsonArray headers)
        {
            foreach (var entry in headers)
            {
                if (entry is not JsonObject header)
                    continue;

                var name = NodeValueAccess.ReadString(header, "name");
                if (string.IsNullOrWhiteSpace(name))
                    continue;

                request.Headers.TryAddWithoutValidation(name, NodeValueAccess.ReadString(header, "value") ?? string.Empty);
            }
        }

        // Pagination header overrides win over the static header list.
        foreach (var (name, value) in overrides)
        {
            request.Headers.Remove(name);
            request.Headers.TryAddWithoutValidation(name, value);
        }
    }

    private async Task<string?> ApplyBodyAsync(
        NodeExecutionContext context, JsonNode? body, HttpRequestMessage request, CancellationToken ct)
    {
        var contentType = NodeValueAccess.ReadString(context.Parameters, "bodyContentType") ?? "json";

        switch (contentType)
        {
            case "json":
                request.Content = new StringContent(body?.ToJsonString() ?? "null", Encoding.UTF8, "application/json");
                return null;

            case "form":
                if (body is not JsonObject form)
                    return "a form body must be a JSON object";
                request.Content = new FormUrlEncodedContent(
                    form.Select(pair => new KeyValuePair<string, string>(pair.Key, NodeValueAccess.ScalarText(pair.Value))));
                return null;

            case "raw":
                request.Content = new StringContent(NodeValueAccess.ScalarText(body), Encoding.UTF8, "text/plain");
                return null;

            case "multipart":
                return await ApplyMultipartAsync(context, body, request, ct);

            case "binary":
                return await ApplyBinaryAsync(context, request, ct);

            default:
                return $"unknown bodyContentType '{contentType}'";
        }
    }

    /// <summary>
    /// Builds a multipart body from the declared fields plus one input binary
    /// attachment. The attachment is streamed from the binary store, so the file
    /// never has to be loaded into item JSON first.
    /// </summary>
    private async Task<string?> ApplyMultipartAsync(
        NodeExecutionContext context, JsonNode? body, HttpRequestMessage request, CancellationToken ct)
    {
        var form = new MultipartFormDataContent();
        if (body is JsonObject fields)
        {
            foreach (var (name, value) in fields)
                form.Add(new StringContent(NodeValueAccess.ScalarText(value), Encoding.UTF8), name);
        }

        var property = NodeValueAccess.ReadString(context.Parameters, "binaryField");
        if (string.IsNullOrWhiteSpace(property))
        {
            request.Content = form;
            return null;
        }

        var attachment = ResolveInputBinary(context, property, out var error);
        if (attachment == null)
        {
            form.Dispose();
            return error;
        }

        var stream = await _binary.OpenAsync(attachment.AssetId, ct);
        if (stream == null)
        {
            form.Dispose();
            return $"binary asset '{attachment.AssetId}' was not found in the binary store";
        }

        var file = new StreamContent(stream);
        if (!string.IsNullOrWhiteSpace(attachment.MimeType))
            file.Headers.ContentType = new MediaTypeHeaderValue(attachment.MimeType);
        form.Add(file, property, attachment.FileName ?? property);

        request.Content = form;
        return null;
    }

    /// <summary>Sends an input binary attachment as the raw request body.</summary>
    private async Task<string?> ApplyBinaryAsync(
        NodeExecutionContext context, HttpRequestMessage request, CancellationToken ct)
    {
        var property = NodeValueAccess.ReadString(context.Parameters, "binaryField") ?? DefaultBinaryProperty;
        var attachment = ResolveInputBinary(context, property, out var error);
        if (attachment == null)
            return error;

        var stream = await _binary.OpenAsync(attachment.AssetId, ct);
        if (stream == null)
            return $"binary asset '{attachment.AssetId}' was not found in the binary store";

        var content = new StreamContent(stream);
        content.Headers.ContentType = new MediaTypeHeaderValue(
            string.IsNullOrWhiteSpace(attachment.MimeType) ? "application/octet-stream" : attachment.MimeType);
        request.Content = content;
        return null;
    }

    /// <summary>
    /// Looks up a named binary attachment on the first input item. A missing item
    /// or property is a body-configuration error, not an empty body.
    /// </summary>
    private static BinaryAttachment? ResolveInputBinary(
        NodeExecutionContext context, string property, out string? error)
    {
        error = null;
        var item = context.Input(0).FirstOrDefault();
        if (item?.Binary == null || !item.Binary.TryGetValue(property, out var attachment))
        {
            error = $"the input item has no binary field '{property}'";
            return null;
        }

        return attachment;
    }
}