design_tweaks.hpp

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#pragma once
 
// pulp::design — the self-describing parameter block an imported/generated
// design carries so that cheap tweaks survive a reload and live in the diff.
//
// An imported artifact (a `ui.js`, a `.dc.html`) embeds one marker-delimited
// block:
//
//     /*EDITMODE-BEGIN*/{"accent":"#33aaff","radius":8}/*EDITMODE-END*/
//
// The block is the artifact's own parameter store. When a human nudges a knob
// in the inspector the host rewrites *only the JSON between the markers*,
// byte-for-byte preserving everything outside it. Because the block is anchored
// content (fixed markers, not a line/offset), it composes with the re-import
// safety loop: a re-import re-emits the surrounding artifact and the persisted
// block is re-applied by key, not by position.
//
// This translation unit is the pure core of that mechanism: locate the block,
// read its parameters, and produce the rewritten artifact text for a changed
// set of parameters. The inspector panel and the send-to-agent affordance are
// UI layers built on top of these primitives and live elsewhere.
//
// Everything here is deterministic and free of I/O so it is unit-testable
// without a window or a render context.
 
#include <optional>
#include <string>
#include <string_view>
#include <vector>
 
namespace pulp::design {

inline constexpr std::string_view kEditBlockBegin = "/*EDITMODE-BEGIN*/";
inline constexpr std::string_view kEditBlockEnd = "/*EDITMODE-END*/";

struct TweakParam {
    std::string key;
    std::string json_value;  
};

struct EditBlockSpan {
    size_t block_begin = 0;    
    size_t block_end = 0;      
    size_t payload_begin = 0;  
    size_t payload_end = 0;    
};

std::optional<EditBlockSpan> find_edit_block(std::string_view text);

std::optional<std::vector<TweakParam>> read_edit_block(std::string_view text);

std::optional<std::string> edit_block_payload(const std::vector<TweakParam>& params);

struct RewriteResult {
    std::string text;             
    bool outside_bytes_intact = false;  
};

std::optional<RewriteResult> rewrite_edit_block(std::string_view text,
                                                const std::vector<TweakParam>& params);

std::optional<RewriteResult> set_edit_param(std::string_view text, std::string_view key,
                                            std::string_view json_value);
 
}  // namespace pulp::design