w4c-workflows-api/Services/Nodes/Executors/HttpRequestNodeExecutor.Pagination.cs

using System.Globalization;
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;

// Pagination half of the HTTP Request node: turns the declarative plan into
// per-page cursor/page-number/next-URL steps and merges query/header/body
// overrides into the next request.

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

    private static JsonNode? ApplyStep(
        HttpPaginationStep step,
        HttpPaginationPlan plan,
        JsonNode? body,
        Dictionary<string, string> queryOverrides,
        Dictionary<string, string> headerOverrides)
    {
        if (step.Cursor != null)
            return ApplyParameter(plan.CursorPlace, plan.CursorName, step.Cursor, body, queryOverrides, headerOverrides);

        if (step.PageNumber is int pageNumber)
            return ApplyParameter(
                plan.PagePlace, plan.PageName,
                pageNumber.ToString(CultureInfo.InvariantCulture),
                body, queryOverrides, headerOverrides);

        return body;
    }

    private static JsonNode? ApplyParameter(
        string place,
        string name,
        string value,
        JsonNode? body,
        Dictionary<string, string> queryOverrides,
        Dictionary<string, string> headerOverrides)
    {
        if (string.IsNullOrEmpty(name))
            return body;

        switch (place)
        {
            case HttpPaginationPlan.PlaceHeader:
                headerOverrides[name] = value;
                return body;

            case HttpPaginationPlan.PlaceBody:
                if (body is JsonObject obj)
                    obj[name] = value;
                else if (body == null)
                    body = new JsonObject { [name] = value };
                return body;

            default:
                queryOverrides[name] = value;
                return body;
        }
    }

    /// <summary>Merges pagination overrides into the base URL query (same-name keys are replaced).</summary>
    private static Uri ApplyQuery(Uri baseUri, IReadOnlyDictionary<string, string> overrides)
    {
        if (overrides.Count == 0)
            return baseUri;

        var pairs = new List<KeyValuePair<string, string>>();
        if (!string.IsNullOrEmpty(baseUri.Query))
        {
            foreach (var part in baseUri.Query.TrimStart('?')
                         .Split('&', StringSplitOptions.RemoveEmptyEntries))
            {
                var separator = part.IndexOf('=');
                var key = separator < 0 ? part : part[..separator];
                var value = separator < 0 ? string.Empty : part[(separator + 1)..];
                pairs.Add(new KeyValuePair<string, string>(
                    Uri.UnescapeDataString(key), Uri.UnescapeDataString(value)));
            }
        }

        foreach (var (name, value) in overrides)
        {
            pairs.RemoveAll(pair => string.Equals(pair.Key, name, StringComparison.Ordinal));
            pairs.Add(new KeyValuePair<string, string>(name, value));
        }

        var query = string.Join('&', pairs.Select(pair =>
            $"{Uri.EscapeDataString(pair.Key)}={Uri.EscapeDataString(pair.Value)}"));

        return new UriBuilder(baseUri) { Query = query }.Uri;
    }

    /// <summary>Resolves a pagination next URL (absolute or relative) and keeps it HTTP(S).</summary>
    private static bool TryResolveNext(string nextUrl, Uri current, out Uri next)
    {
        next = null!;
        try
        {
            // A leading-slash path parses as an absolute "file" URI on Unix, so
            // only an explicitly http(s) absolute URL bypasses relative resolution.
            if (Uri.TryCreate(nextUrl, UriKind.Absolute, out var absolute)
                && absolute.Scheme is "http" or "https")
            {
                next = absolute;
            }
            else
            {
                next = new Uri(current, nextUrl);
            }

            return next.Scheme is "http" or "https";
        }
        catch (UriFormatException)
        {
            return false;
        }
    }

    /// <summary>Accumulates a page under the item cap; returns true when the cap is reached.</summary>
    private static bool AddItems(List<FlowItem> items, IReadOnlyList<FlowItem> pageItems, int maxItems)
    {
        if (maxItems <= 0)
        {
            items.AddRange(pageItems);
            return false;
        }

        var remaining = maxItems - items.Count;
        if (remaining <= 0)
            return true;

        if (pageItems.Count > remaining)
        {
            items.AddRange(pageItems.Take(remaining));
            return true;
        }

        items.AddRange(pageItems);
        return items.Count >= maxItems;
    }
}