From 06adba28b4f9f07d3c8078ce02bdeb00b29e97ea Mon Sep 17 00:00:00 2001
From: zeropol <tn.zeropol@gmail.com>
Date: Thu, 1 Apr 2021 03:58:53 +0200
Subject: [PATCH] Filter items by book skill ( V, e, / ), fixes #47530 (#48275)

* Add a filter to search books by skills they teach

* Hide books not skimmed when filtering items

The player was able to know which skill a book tech without first skim it.

* Fix typographic error

* Check non-skill by ID

name() is i18n-dependent and it may return something other than "nothing" in different languages.

Co-authored-by: Binrui Dong <brett.browning.dong@gmail.com>
---
 src/item.cpp        | 10 ++++++++++
 src/item.h          |  2 ++
 src/item_search.cpp | 10 ++++++++++
 src/output.cpp      |  5 +++--
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/item.cpp b/src/item.cpp
index 012a7e7d8f17b..5bac244aa48bb 100644
--- a/src/item.cpp
+++ b/src/item.cpp
@@ -7099,6 +7099,16 @@ bool item::is_book() const
     return !!type->book;
 }
 
+std::string item::get_book_skill() const
+{
+    if( is_book() ) {
+        if( type->book->skill->ident() != skill_id::NULL_ID() ) {
+            return type->book->skill->name();
+        }
+    }
+    return "";
+}
+
 bool item::is_map() const
 {
     return get_category_shallow().get_id() == item_category_maps;
diff --git a/src/item.h b/src/item.h
index 9569cade94e2c..75ccd1f5c0602 100644
--- a/src/item.h
+++ b/src/item.h
@@ -1243,6 +1243,8 @@ class item : public visitable
         /** Returns true if the item is A: is SOLID and if it B: is of type LIQUID */
         bool is_frozen_liquid() const;
 
+        /** Returns empty string if the book teach no skill */
+        std::string get_book_skill() const;
         float get_specific_heat_liquid() const;
         float get_specific_heat_solid() const;
         float get_latent_heat() const;
diff --git a/src/item_search.cpp b/src/item_search.cpp
index fd6b92bd44d22..04ff020e4a3e0 100644
--- a/src/item_search.cpp
+++ b/src/item_search.cpp
@@ -3,7 +3,9 @@
 #include <map>
 #include <utility>
 
+#include "avatar.h"
 #include "cata_utility.h"
+#include "game.h"
 #include "item.h"
 #include "item_category.h"
 #include "material.h"
@@ -68,6 +70,14 @@ std::function<bool( const item & )> basic_item_filter( std::string filter )
                 const std::string note = i.get_var( "item_note" );
                 return !note.empty() && lcmatch( note, filter );
             };
+        // by book skill
+        case 's':
+            return [filter]( const item & i ) {
+                if( get_avatar().has_identified( i.typeId() ) ) {
+                    return lcmatch( i.get_book_skill(), filter );
+                }
+                return false;
+            };
         // by name
         default:
             return [filter]( const item & a ) {
diff --git a/src/output.cpp b/src/output.cpp
index cdd163a12ce1f..545cbf00c5e07 100644
--- a/src/output.cpp
+++ b/src/output.cpp
@@ -870,11 +870,12 @@ void draw_item_filter_rules( const catacurses::window &win, int starty, int heig
 
     starty += fold_and_print( win, point( 1, starty ), len, c_white,
                               _( "Search [<color_yellow>c</color>]ategory, [<color_yellow>m</color>]aterial, "
-                                 "[<color_yellow>q</color>]uality, [<color_yellow>n</color>]otes or "
+                                 "[<color_yellow>q</color>]uality, [<color_yellow>n</color>]otes, "
+                                 "[<color_yellow>s</color>]skill taught by books or "
                                  "[<color_yellow>d</color>]isassembled components." ) );
     fold_and_print( win, point( 1, starty ), len, c_white,
                     //~ An example of how to filter items based on category or material.
-                    _( "Examples: c:food,m:iron,q:hammering,n:toolshelf,d:pipe" ) );
+                    _( "Examples: c:food,m:iron,q:hammering,n:toolshelf,d:pipe,s:devices" ) );
     wnoutrefresh( win );
 }