diff --git a/version0/list.hpp b/version0/list.hpp new file mode 100644 index 0000000..9bb16ec --- /dev/null +++ b/version0/list.hpp @@ -0,0 +1,218 @@ +#include +#include +#include +#include +#include + +#include + +namespace GreenCRDT { + +template +struct List { + struct ListID { + AgentType id; + uint64_t seq{0}; // strictly increasing for that agent + + bool operator<(const ListID& rhs) const { + if (seq < rhs.seq) { + return true; + } else if (seq > rhs.seq) { + return false; + } else { // == + return id < rhs.id; + } + } + + bool operator==(const ListID& rhs) const { + return seq == rhs.seq && id == rhs.id; + } + + bool operator!=(const ListID& rhs) const { + return seq != rhs.seq || id != rhs.id; + } + }; + + // TODO: replace with SoA + struct Entry { + ListID id; + + // Yjs + std::optional parent_left; + std::optional parent_right; + + // might be deleted (yes, *sigh*, crtds need tombstones) + std::optional value; + }; + + // TODO: use something better + std::vector list; + + // number of not deleted entries + size_t doc_size {0}; + + std::map last_seen_seq; + + std::optional findIdx(const ListID& list_id) { + for (size_t i = 0; i < list.size(); i++) { + if (list[i].id == list_id) { + return i; + } + } + + return std::nullopt; + } + + // returns false if missing OPs + // based on YjsMod https://github.com/josephg/reference-crdts/blob/9f4f9c3a97b497e2df8ae4473d1e521d3c3bf2d2/crdts.ts#L293-L348 + // which is a modified Yjs(YATA) algo + bool add(const ListID& list_id, const ValueType& value, const std::optional& parent_left, const std::optional& parent_right) { + // check agent op order + if (!last_seen_seq.count(list_id.id)) { + // we dont know this agent yet, first seq needs to be 0 + if (list_id.seq != 0) { + return false; + } + } else { + // making sure we dont skip operations by that agent + if (list_id.seq != last_seen_seq.at(list_id.id) + 1) { + return false; + } + } + + if (list.empty()) { + if (parent_left.has_value() || parent_right.has_value()) { + // empty, missing parents + return false; + } + + // insert parentless into empty doc + list.emplace(list.begin(), Entry{ + list_id, + parent_left, + parent_right, + value + }); + } else { + // find left + std::optional left_idx = std::nullopt; + size_t insert_idx = 0; + if (parent_left.has_value()) { + left_idx = findIdx(parent_left.value()); + if (!left_idx.has_value()) { + // missing parent left + return false; + } + + // we insert before the it, so we need to go past the left parent + insert_idx = left_idx.value() + 1; + } // else insert_idx = 0 + + // find right + size_t right_idx = list.size(); + if (parent_right.has_value()) { + auto tmp_right = findIdx(parent_right.value()); + if (!tmp_right.has_value()) { + return false; + } + right_idx = tmp_right.value(); + } + + bool scanning {false}; + + for(size_t i = insert_idx;; i++) { + if (!scanning) { + insert_idx = i; + } + // if right parent / end of doc, insert + if (insert_idx == right_idx) { + break; + } + // we ran past right o.o ? + if (insert_idx == list.size()) { + break; + } + + const Entry& at_i = list[i]; + // parents left and right + std::optional i_left_idx {std::nullopt}; + if (at_i.parent_left.has_value()) { + i_left_idx = findIdx(at_i.parent_left.value()); + if (!i_left_idx.has_value()) { + assert(false && "item in list with unknown parent left!!"); + return false; + } + } + + // possibility map + // + // | ir < r | ir == r | ir > r + // ------------------------------------- + // il < l | insert | insert | insert + // il == l | ? | agentfallback | ? + // il > l | skip | skip | skip + + if (i_left_idx < left_idx) { + break; + } else if (i_left_idx == left_idx) { + // get i parent_right + size_t i_right_idx = list.size(); + if (at_i.parent_right.has_value()) { + auto tmp_right = findIdx(at_i.parent_right.value()); + if (!tmp_right.has_value()) { + assert(false && "item in list with unknown parent right!!"); + return false; + } + i_right_idx = tmp_right.value(); + } + + if (i_right_idx < right_idx) { + scanning = true; + } else if (i_right_idx == right_idx) { + // agent id tie breaker + if (list_id.id < at_i.id.id) { + break; + } else { + scanning = false; + } + } else { // i_right_idx > right_idx + scanning = false; + } + } else { // il > l + // do nothing + } + } + + list.emplace(list.begin() + insert_idx, Entry{ + list_id, + parent_left, + parent_right, + value + }); + } + + doc_size++; + last_seen_seq[list_id.id] = list_id.seq; + return true; + } + + // returns false if not found + bool del(const ListID& id) { + auto it = list.begin(); + for (; it != list.end(); it++) { + if (it->id == id) { + it->value = std::nullopt; + + assert(doc_size > 0); + doc_size--; + return true; + } + } + + // not found + return false; + } +}; + +} // GreenCRDT + diff --git a/version0/text_document.hpp b/version0/text_document.hpp new file mode 100644 index 0000000..6b02eab --- /dev/null +++ b/version0/text_document.hpp @@ -0,0 +1,31 @@ +#include "./list.hpp" + +namespace GreenCRDT { + +template +struct TextDocument { + // TODO: determine if char is the best + using ListType = List; + + struct Cursor { + AgentType who; + typename ListType::ListID pos; + }; + + ListType state; + + std::string getText(void) { + std::string text; + + for (const auto& it : state.list) { + if (it.value) { + text += it.value.value(); + } + } + + return text; + } +}; + +} // GreenCRDT +