#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();
    }

    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;

        if (def->kind == DagKind::Blend) {
            out << "vec4 node_" << i << "(vec4 a, vec4 b, vec2 uv) {\n";
        } else {
            out << "vec4 node_" << i << "(vec4 c, 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";
    out << "    vec4 c = vec4(0.04, 0.04, 0.06, 1.0);\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) {
            out << "    vec4 out_" << i << " = (i > 0 ? out_" << (i-1) << " : c);\n";
            continue;
        }

        std::string prev = (i == 0) ? "vec4(0.0, 0.0, 0.0, 1.0)" : "out_" + std::to_string(i - 1);

        if (def->kind == DagKind::Blend) {
            int src_idx = -1;
            if (!step.source_id.empty()) {
                for (int j = 0; j < i; ++j) {
                    if (pipeline[static_cast<size_t>(j)].id == step.source_id) {
                        src_idx = j;
                        break;
                    }
                }
            }
            if (src_idx < 0 || src_idx >= i) {
                src_idx = std::max(0, i - 2);
            }
            std::string src;
            if (i == 0) {
                src = prev;
            } else {
                src = "out_" + std::to_string(std::min(src_idx, i - 1));
            }
            out << "    vec4 out_" << i << " = node_" << i << "(" << prev << ", " << src << ", uv);\n";
        } else {
            out << "    vec4 out_" << i << " = node_" << i << "(" << prev << ", uv);\n";
        }
    }

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

    return out.str();
}

} // namespace fn::gfx