+/* Size of rev graph with no "padding" columns */
+#define SIZEOF_REVITEMS (SIZEOF_REVGRAPH - (SIZEOF_REVGRAPH / 2))
+
+struct rev_graph {
+ struct rev_graph *prev, *next, *parents;
+ char rev[SIZEOF_REVITEMS][SIZEOF_REV];
+ size_t size;
+ struct commit *commit;
+ size_t pos;
+};
+
+/* Parents of the commit being visualized. */
+static struct rev_graph graph_parents[4];
+
+/* The current stack of revisions on the graph. */
+static struct rev_graph graph_stacks[4] = {
+ { &graph_stacks[3], &graph_stacks[1], &graph_parents[0] },
+ { &graph_stacks[0], &graph_stacks[2], &graph_parents[1] },
+ { &graph_stacks[1], &graph_stacks[3], &graph_parents[2] },
+ { &graph_stacks[2], &graph_stacks[0], &graph_parents[3] },
+};
+
+static inline bool
+graph_parent_is_merge(struct rev_graph *graph)
+{
+ return graph->parents->size > 1;
+}
+
+static inline void
+append_to_rev_graph(struct rev_graph *graph, chtype symbol)
+{
+ struct commit *commit = graph->commit;
+
+ if (commit->graph_size < ARRAY_SIZE(commit->graph) - 1)
+ commit->graph[commit->graph_size++] = symbol;
+}
+
+static void
+done_rev_graph(struct rev_graph *graph)
+{
+ if (graph_parent_is_merge(graph) &&
+ graph->pos < graph->size - 1 &&
+ graph->next->size == graph->size + graph->parents->size - 1) {
+ size_t i = graph->pos + graph->parents->size - 1;
+
+ graph->commit->graph_size = i * 2;
+ while (i < graph->next->size - 1) {
+ append_to_rev_graph(graph, ' ');
+ append_to_rev_graph(graph, '\\');
+ i++;
+ }
+ }
+
+ graph->size = graph->pos = 0;
+ graph->commit = NULL;
+ memset(graph->parents, 0, sizeof(*graph->parents));
+}
+
+static void
+push_rev_graph(struct rev_graph *graph, char *parent)
+{
+ int i;
+
+ /* "Collapse" duplicate parents lines.
+ *
+ * FIXME: This needs to also update update the drawn graph but
+ * for now it just serves as a method for pruning graph lines. */
+ for (i = 0; i < graph->size; i++)
+ if (!strncmp(graph->rev[i], parent, SIZEOF_REV))
+ return;
+
+ if (graph->size < SIZEOF_REVITEMS) {
+ string_ncopy(graph->rev[graph->size++], parent, SIZEOF_REV);
+ }
+}
+
+static chtype
+get_rev_graph_symbol(struct rev_graph *graph)
+{
+ chtype symbol;
+
+ if (graph->parents->size == 0)
+ symbol = REVGRAPH_INIT;
+ else if (graph_parent_is_merge(graph))
+ symbol = REVGRAPH_MERGE;
+ else if (graph->pos >= graph->size)
+ symbol = REVGRAPH_BRANCH;
+ else
+ symbol = REVGRAPH_COMMIT;
+
+ return symbol;
+}
+
+static void
+draw_rev_graph(struct rev_graph *graph)
+{
+ struct rev_filler {
+ chtype separator, line;
+ };
+ enum { DEFAULT, RSHARP, RDIAG, LDIAG };
+ static struct rev_filler fillers[] = {
+ { ' ', REVGRAPH_LINE },
+ { '`', '.' },
+ { '\'', ' ' },
+ { '/', ' ' },
+ };
+ chtype symbol = get_rev_graph_symbol(graph);
+ struct rev_filler *filler;
+ size_t i;
+
+ filler = &fillers[DEFAULT];
+
+ for (i = 0; i < graph->pos; i++) {
+ append_to_rev_graph(graph, filler->line);
+ if (graph_parent_is_merge(graph->prev) &&
+ graph->prev->pos == i)
+ filler = &fillers[RSHARP];
+
+ append_to_rev_graph(graph, filler->separator);
+ }
+
+ /* Place the symbol for this revision. */
+ append_to_rev_graph(graph, symbol);
+
+ if (graph->prev->size > graph->size)
+ filler = &fillers[RDIAG];
+ else
+ filler = &fillers[DEFAULT];
+
+ i++;
+
+ for (; i < graph->size; i++) {
+ append_to_rev_graph(graph, filler->separator);
+ append_to_rev_graph(graph, filler->line);
+ if (graph_parent_is_merge(graph->prev) &&
+ i < graph->prev->pos + graph->parents->size)
+ filler = &fillers[RSHARP];
+ if (graph->prev->size > graph->size)
+ filler = &fillers[LDIAG];
+ }
+
+ if (graph->prev->size > graph->size) {
+ append_to_rev_graph(graph, filler->separator);
+ if (filler->line != ' ')
+ append_to_rev_graph(graph, filler->line);
+ }
+}
+
+/* Prepare the next rev graph */
+static void
+prepare_rev_graph(struct rev_graph *graph)
+{
+ size_t i;
+
+ /* First, traverse all lines of revisions up to the active one. */
+ for (graph->pos = 0; graph->pos < graph->size; graph->pos++) {
+ if (!strcmp(graph->rev[graph->pos], graph->commit->id))
+ break;
+
+ push_rev_graph(graph->next, graph->rev[graph->pos]);
+ }
+
+ /* Interleave the new revision parent(s). */
+ for (i = 0; i < graph->parents->size; i++)
+ push_rev_graph(graph->next, graph->parents->rev[i]);
+
+ /* Lastly, put any remaining revisions. */
+ for (i = graph->pos + 1; i < graph->size; i++)
+ push_rev_graph(graph->next, graph->rev[i]);
+}
+
+static void
+update_rev_graph(struct rev_graph *graph)
+{
+ /* If this is the finalizing update ... */
+ if (graph->commit)
+ prepare_rev_graph(graph);
+
+ /* Graph visualization needs a one rev look-ahead,
+ * so the first update doesn't visualize anything. */
+ if (!graph->prev->commit)
+ return;
+
+ draw_rev_graph(graph->prev);
+ done_rev_graph(graph->prev->prev);
+}
+
+
+/*
+ * Main view backend
+ */
+