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;

// Response half of the HTTP Request node: maps a page body to output items,
// including the file/binary case and the envelope-unwrapping JSON path.

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

    private sealed record BuildResult(List<FlowItem> Items, string? Error);

    /// <summary>
    /// Maps one page's body to items. <c>responseFormat: file</c> is the only
    /// asynchronous case: it stores the payload and emits a binary-backed item.
    /// </summary>
    private async Task<BuildResult> BuildItemsAsync(
        PageResult page,
        string responseFormat,
        string? putOutputInField,
        string? outputPath,
        CancellationToken ct)
    {
        if (responseFormat == "file")
        {
            BinaryAttachment attachment;
            try
            {
                await using var content = new MemoryStream(page.Bytes, writable: false);
                attachment = await _binary.SaveAsync(content, page.SuggestedFileName, page.ContentType, ct);
            }
            catch (OperationCanceledException)
            {
                throw;
            }
            catch (Exception ex) when (ex is InvalidOperationException or IOException)
            {
                return new BuildResult(new List<FlowItem>(), ex.Message);
            }

            return new BuildResult(new List<FlowItem> { FileItem(attachment, putOutputInField) }, null);
        }

        if (!TryBuildItems(
                page.Body, page.Parsed, responseFormat, putOutputInField, outputPath,
                out var items, out var error))
        {
            return new BuildResult(new List<FlowItem>(), error);
        }

        return new BuildResult(items, null);
    }

    /// <summary>Builds a one-item result whose payload lives in the binary store.</summary>
    private static FlowItem FileItem(BinaryAttachment attachment, string? putOutputInField)
    {
        var meta = new JsonObject
        {
            ["fileName"] = attachment.FileName,
            ["mimeType"] = attachment.MimeType,
            ["sizeBytes"] = attachment.SizeBytes,
        };

        var extension = Path.GetExtension(attachment.FileName);
        if (!string.IsNullOrEmpty(extension))
            meta["fileExtension"] = extension.TrimStart('.');

        return new FlowItem
        {
            Json = string.IsNullOrWhiteSpace(putOutputInField)
                ? meta
                : new JsonObject { [putOutputInField!] = meta },
            Binary = new Dictionary<string, BinaryAttachment>(StringComparer.Ordinal)
            {
                [DefaultBinaryProperty] = attachment,
            },
        };
    }

    /// <summary>
    /// File name for a downloaded response: the Content-Disposition name, else the
    /// last URL path segment, else null. Directory separators are stripped so a
    /// provider cannot smuggle a path into the stored reference.
    /// </summary>
    private static string? ResolveFileName(HttpResponseMessage response, Uri requestUri)
    {
        try
        {
            var disposition = response.Content.Headers.ContentDisposition;
            var name = TrimName(disposition?.FileNameStar ?? disposition?.FileName);
            if (name != null)
                return name;
        }
        catch (FormatException)
        {
            // Malformed Content-Disposition: fall through to the URL segment.
        }

        if (requestUri.Segments.Length > 0)
        {
            var name = TrimName(Uri.UnescapeDataString(requestUri.Segments[^1]));
            if (name != null)
                return name;
        }

        return null;
    }

    private static string? TrimName(string? name)
    {
        if (string.IsNullOrWhiteSpace(name))
            return null;

        var trimmed = name.Trim().Trim('"');
        var separator = trimmed.LastIndexOfAny(new[] { '/', '\\' });
        if (separator >= 0)
            trimmed = trimmed[(separator + 1)..];
        return string.IsNullOrWhiteSpace(trimmed) ? null : trimmed;
    }

    private static bool TryBuildItems(
        string body,
        JsonNode? parsed,
        string responseFormat,
        string? putOutputInField,
        string? outputPath,
        out List<FlowItem> items,
        out string? error)
    {
        items = new List<FlowItem>();
        error = null;

        switch (responseFormat)
        {
            case "text":
                items.Add(TextItem(body, putOutputInField));
                return true;

            case "json":
                if (parsed == null)
                {
                    error = "the response is not valid JSON";
                    return false;
                }
                break;

            case "file":
                // File responses are handled by BuildItemsAsync before this point.
                error = "responseFormat 'file' must be built through the binary store";
                return false;

            default: // autodetect
                if (parsed == null)
                {
                    items.Add(TextItem(body, putOutputInField));
                    return true;
                }
                break;
        }

        // Envelope unwrapping: read the page's items from a JSON path so the
        // cursor/next fields that live beside them do not become items.
        if (!string.IsNullOrWhiteSpace(outputPath) && parsed is JsonObject envelope)
        {
            parsed = NodePath.Read(envelope, outputPath, dotNotation: true);
            if (parsed == null)
                return true; // a page without the data field simply contributes nothing
        }

        items.AddRange(ToItems(parsed, putOutputInField));
        return true;
    }

    private static List<FlowItem> ToItems(JsonNode parsed, string? putOutputInField)
    {
        var items = new List<FlowItem>();
        if (!string.IsNullOrWhiteSpace(putOutputInField))
        {
            if (parsed is JsonArray wrapped)
            {
                foreach (var element in wrapped)
                    items.Add(Wrap(new JsonObject { [putOutputInField] = element?.DeepClone() }));
            }
            else
            {
                items.Add(Wrap(new JsonObject { [putOutputInField] = parsed.DeepClone() }));
            }
            return items;
        }

        switch (parsed)
        {
            case JsonArray array:
                foreach (var element in array)
                {
                    if (element is JsonObject obj)
                        items.Add(Wrap(obj));
                    else
                        items.Add(Wrap(new JsonObject { ["value"] = element?.DeepClone() }));
                }
                break;

            case JsonObject obj:
                items.Add(Wrap(obj));
                break;

            default:
                items.Add(Wrap(new JsonObject { ["value"] = parsed.DeepClone() }));
                break;
        }

        return items;
    }

    private static FlowItem TextItem(string body, string? putOutputInField)
        => string.IsNullOrWhiteSpace(putOutputInField)
            ? Wrap(new JsonObject { ["data"] = body })
            : Wrap(new JsonObject { [putOutputInField] = body });

    private static FlowItem Wrap(JsonNode json)
        => new() { Json = json is JsonObject obj ? (JsonObject)obj.DeepClone() : new JsonObject { ["value"] = json } };
}