#include "gfx/dag_compile.h"
#include "gfx/dag_catalog.h"
#include <algorithm>
#include <sstream>

namespace fn::gfx {

static constexpr int MAX_NODES = 16;

std::string compile_dag_to_glsl(const std::vector<DagStep>& pipeline) {
    const int n = static_cast<int>(std::min(pipeline.size(), static_cast<size_t>(MAX_NODES)));
    std::ostringstream out;

    out << "uniform vec4 u_params[16];\n\n";

    if (n == 0) {
        out << "void main() {\n";
        out << "    vec2 uv = gl_FragCoord.xy / u_resolution;\n";
        out << "    (void)uv;\n";
        out << "    fragColor = vec4(0.04, 0.04, 0.06, 1.0);\n";
        out << "}\n";
        return out.str();
    }

    // Emit per-node functions with signatures based on num_inputs
    for (int i = 0; i < n; ++i) {
        const DagStep& step = pipeline[static_cast<size_t>(i)];
        const DagNodeDef* def = dag_find(step.name);
        if (!def) continue;

        int ni = def->num_inputs;
        out << "vec4 node_" << i << "(";
        if (ni >= 1) out << "vec4 a";
        if (ni >= 2) out << ", vec4 b";
        if (ni >= 3) out << ", vec4 c";
        if (ni >= 4) out << ", vec4 d";
        if (ni > 0)  out << ", ";
        out << "vec2 uv) {\n";
        out << def->body_glsl(i) << "\n";
        out << "}\n\n";
    }

    out << "void main() {\n";
    out << "    vec2 uv = gl_FragCoord.xy / u_resolution;\n";

    for (int i = 0; i < n; ++i) {
        const DagStep& step = pipeline[static_cast<size_t>(i)];
        const DagNodeDef* def = dag_find(step.name);
        if (!def) {
            if (i == 0) {
                out << "    vec4 out_" << i << " = vec4(0.0, 0.0, 0.0, 1.0);\n";
            } else {
                out << "    vec4 out_" << i << " = out_" << (i - 1) << ";\n";
            }
            continue;
        }

        int ni = def->num_inputs;

        // Resolve each input slot
        // For slot k: look for source_ids[k] in pipeline[0..i-1]; fallback = prev output
        auto resolve = [&](int k) -> std::string {
            const std::string& sid = step.source_ids[static_cast<size_t>(k)];
            if (!sid.empty()) {
                for (int j = 0; j < i; ++j) {
                    if (pipeline[static_cast<size_t>(j)].id == sid) {
                        return "out_" + std::to_string(j);
                    }
                }
            }
            // fallback
            if (i == 0) return "vec4(0.0, 0.0, 0.0, 1.0)";
            return "out_" + std::to_string(i - 1);
        };

        out << "    vec4 out_" << i << " = node_" << i << "(";
        for (int k = 0; k < ni; ++k) {
            if (k > 0) out << ", ";
            out << resolve(k);
        }
        if (ni > 0) out << ", ";
        out << "uv);\n";
    }

    out << "    fragColor = out_" << (n - 1) << ";\n";
    out << "}\n";

    return out.str();
}

} // namespace fn::gfx