common: add partial regex support (#12808)

* move string_find_partial_stop & string_ends_with to common

* add common_regex (supports partial matches)

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* Update common/regex-partial.cpp

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* Update common/regex-partial.cpp

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* Update common/regex-partial.h

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* partial regex: add missing iterator end checks

* string utils: use string_views

* direct throw to avoid ggml.h include

* regex-partial: replace missed ggml_asserts

---------

Co-authored-by: ochafik <ochafik@google.com>
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

common/regex-partial.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <regex>
+#include <string>
+
+enum common_regex_match_type {
+    COMMON_REGEX_MATCH_TYPE_NONE,
+    COMMON_REGEX_MATCH_TYPE_PARTIAL,
+    COMMON_REGEX_MATCH_TYPE_FULL,
+};
+
+struct common_string_range {
+    size_t begin;
+    size_t end;
+    common_string_range(size_t begin, size_t end) : begin(begin), end(end) {
+        if (begin > end) {
+            throw std::runtime_error("Invalid range");
+        }
+    }
+    // prevent default ctor
+    common_string_range() = delete;
+    bool empty() const {
+        return begin == end;
+    }
+    bool operator==(const common_string_range & other) const {
+        return begin == other.begin && end == other.end;
+    }
+};
+
+struct common_regex_match {
+    common_regex_match_type type = COMMON_REGEX_MATCH_TYPE_NONE;
+    std::vector<common_string_range> groups;
+
+    bool operator==(const common_regex_match & other) const {
+        return type == other.type && groups == other.groups;
+    }
+    bool operator!=(const common_regex_match & other) const {
+        return !(*this == other);
+    }
+};
+
+class common_regex {
+    std::string pattern;
+    std::regex rx;
+    std::regex rx_reversed_partial;
+
+  public:
+    explicit common_regex(const std::string & pattern);
+
+    common_regex_match search(const std::string & input, size_t pos, bool as_match = false) const;
+
+    const std::string & str() const { return pattern; }
+};
+
+// For testing only (pretty print of failures).
+std::string regex_to_reversed_partial_regex(const std::string & pattern);