Update readme

README.md

@@ -1,34 +1,431 @@
-# dbc parser skeleton
+DBC Parser Documentation
+Overview
 
-A minimal DBC parser skeleton for the **FrameTap** project.
+This module implements a minimal DBC parser intended for use in the FrameTap project.
 
-The purpose of this module is to read a DBC file and convert it into a simple internal representation that can later be:
+Its purpose is to read a DBC file and convert it into an internal representation that can later be used for:
 
-- displayed as a tree
+    displaying CAN frames and signals
-- connected to `Qt Model/View`
-- used for signal selection
-- extended toward runtime CAN frame decoding
 
----
+    building a hierarchical structure for UI
 
-## Overview
+    integrating with Qt Model/View
 
-The architecture is intentionally simple:
+    selecting signals for plotting
 
-1. `dbc_parser` reads a DBC file
+    preparing for runtime CAN/J1939 decoding
-2. parsed data is stored in `DbcDatabase`
-3. `dbc_tree_builder` converts it into a `TreeNode` hierarchy
-4. the resulting tree can later be adapted to `QAbstractItemModel`
 
-This keeps the parser independent from Qt and makes it easier to test and evolve.
+The implementation intentionally follows the KISS principle:
 
----
+    simple
 
-## Currently supported
+    readable
 
-### Frame definitions
+    easy to modify
 
-Supported frame lines:
+    independent from Qt
+
+This is not a full DBC parser, but a practical foundation that can be extended gradually.
+Architecture
+
+The module uses a simple processing pipeline.
+
+DBC file
+   ↓
+DbcParser
+   ↓
+DbcDatabase
+   ↓
+DbcTreeBuilder
+   ↓
+TreeNode hierarchy
+   ↓
+Future Qt Model/View integration
+
+Each component has a clear responsibility.
+Component	Responsibility
+DbcParser	Reads and parses the DBC file
+DbcDatabase	Stores parsed frames and signals
+DbcTreeBuilder	Converts the database into a tree
+TreeNode	Represents hierarchical nodes
+
+This separation allows the parser to remain independent from UI or visualization logic.
+File Structure
+
+The module consists of several logical parts.
+Data structures
+
+Files:
+
+signal_info.h
+frame_info.h
+dbc_database.h
+
+These files define the internal representation of parsed data.
+Tree representation
+
+Files:
+
+tree_node.h
+tree_node.cpp
+
+Defines a simple hierarchical structure that can later be used by UI components.
+Parser
+
+Files:
+
+dbc_parser.h
+dbc_parser.cpp
+
+Responsible for reading the DBC file and extracting frame and signal information.
+Tree builder
+
+Files:
+
+dbc_tree_builder.h
+dbc_tree_builder.cpp
+
+Converts the parsed database into a tree representation.
+Data Structures
+SignalInfo
+
+Represents a single signal defined in a DBC file.
+
+Fields:
+
+name
+startBit
+length
+isLittleEndian
+isSigned
+factor
+offset
+minimum
+maximum
+unit
+receivers
+comment
+
+Notes:
+
+    receivers may contain multiple ECUs
+
+    comment is optional
+
+    factor and offset define physical conversion
+
+Physical value is calculated as:
+
+physical = raw * factor + offset
+
+FrameInfo
+
+Represents a CAN frame.
+
+Fields:
+
+name
+canId
+dlc
+transmitter
+comment
+signals
+pgn
+hasPgn
+
+Notes:
+
+    signals is a vector of SignalInfo
+
+    transmitter is the ECU that sends the frame
+
+    pgn is derived if the frame appears to follow J1939 rules
+
+DbcDatabase
+
+Top level container for parsed data.
+
+DbcDatabase
+ └── vector<FrameInfo>
+
+This structure represents the entire DBC file content.
+Tree Representation
+
+The module converts the parsed data into a tree.
+
+Node types:
+
+Root
+Frame
+Signal
+
+Example structure:
+
+dbc
+ ├── EngineData
+ │    ├── EngineSpeed
+ │    ├── OilTemp
+ │    └── CoolantTemp
+ └── VehicleData
+      ├── VehicleSpeed
+      └── Odometer
+
+Each node stores either:
+
+    FrameInfo
+
+    SignalInfo
+
+This tree structure is designed to integrate easily with Qt Model/View.
+Parser
+
+The parser is implemented in:
+
+dbc_parser.h
+dbc_parser.cpp
+
+It performs line-based parsing of the DBC file.
+
+Supported elements:
+
+BO_
+SG_
+CM_
+
+Supported DBC Syntax
+Frame Definition
+
+Example:
 
-```text
 BO_ 256 EngineData: 8 EEC1
+
+Parsed values:
+Field	Meaning
+256	CAN identifier
+EngineData	frame name
+8	DLC
+EEC1	transmitter ECU
+Signal Definition
+
+Example:
+
+SG_ EngineSpeed : 0|16@1+ (0.125,0) [0|8000] "rpm" ECU1,ECU2
+
+Parsed values:
+Field	Meaning
+EngineSpeed	signal name
+0	start bit
+16	signal length
+@1	little endian
++	unsigned
+factor	0.125
+offset	0
+minimum	0
+maximum	8000
+unit	rpm
+receivers	ECU1, ECU2
+Comments
+
+Frame comment:
+
+CM_ BO_ 256 "Engine data frame";
+
+Signal comment:
+
+CM_ SG_ 256 EngineSpeed "Actual engine speed";
+
+These values are stored in:
+
+FrameInfo::comment
+SignalInfo::comment
+
+PGN Extraction
+
+PGN is derived using simplified J1939 logic.
+
+Typical J1939 identifier layout:
+
+Priority
+Reserved
+Data Page
+PDU Format
+PDU Specific
+Source Address
+
+The parser extracts PGN from the 29-bit CAN ID.
+
+This is a simplified approximation and should not be considered full J1939 validation.
+Example Usage
+
+Typical usage:
+
+DbcParser parser;
+
+DbcDatabase database = parser.ParseFile("example.dbc");
+
+DbcTreeBuilder builder;
+
+std::unique_ptr<TreeNode> root = builder.Build(database);
+
+After this step, the tree can be used by a UI or visualization system.
+Example Tree
+
+Example output structure:
+
+dbc
+ ├── EngineData
+ │    ├── EngineSpeed
+ │    ├── OilTemp
+ │    └── CoolantTemp
+ └── VehicleData
+      ├── VehicleSpeed
+      └── Odometer
+
+Limitations
+
+The current implementation intentionally does not support many advanced DBC features.
+
+Not supported yet:
+
+multiplexed signals
+BA_ attributes
+BA_DEF_ definitions
+VAL_ value tables
+signal groups
+advanced comments
+complex syntax variations
+
+These can be added later if required.
+Design Principles
+KISS
+
+The parser is intentionally simple.
+
+It avoids complex grammar systems and tokenizers in order to keep the code easy to understand and maintain.
+Separation of Concerns
+
+Parsing, storage, and tree building are separate components.
+
+This makes it easier to:
+
+    test the parser
+
+    change UI representation
+
+    export data
+
+    reuse the module elsewhere
+
+Qt Independence
+
+The parser itself does not depend on Qt.
+
+Qt integration should be implemented through a separate adapter layer.
+Future Development
+
+Recommended evolution path.
+Stage 1 (current)
+
+BO_
+SG_
+CM_
+transmitter
+receivers
+basic PGN extraction
+tree representation
+
+Stage 2
+
+Add:
+
+extended CAN ID detection
+better PGN extraction
+TreeNode parent pointer
+Qt Model adapter
+
+Stage 3
+
+Add support for:
+
+VAL_ value tables
+BA_ attributes
+BA_DEF_ definitions
+extended comments
+
+Stage 4
+
+Advanced functionality:
+
+multiplexing
+runtime signal decoding
+integration with CAN stream
+drag-and-drop plotting
+
+Intended Usage in FrameTap
+
+This module will allow FrameTap to:
+
+load DBC files
+display frames and signals
+select signals
+search signals
+display metadata
+prepare runtime decoding
+
+Example workflow:
+
+Load DBC
+   ↓
+Browse signals
+   ↓
+Select signal
+   ↓
+Decode CAN frames
+   ↓
+Plot physical values
+
+Why Abstract Factory Is Not Used
+
+An abstract factory is intentionally not used at this stage.
+
+The current structure already separates responsibilities clearly:
+
+parser → database → tree builder → tree
+
+Introducing factories now would increase complexity without significant benefit.
+
+Factories can be added later if multiple internal representations are required.
+Build Integration
+
+The module is independent of any specific build system.
+
+It can be integrated using:
+
+CMake
+qmake
+Makefile
+
+Simply add the source files to the project.
+Summary
+
+This module provides a minimal but extensible DBC parser designed for FrameTap.
+
+Key properties:
+
+simple
+modular
+Qt-independent
+extendable
+
+It converts a DBC file into an internal structure:
+
+frame → signals
+
+with additional metadata such as:
+
+transmitter
+receivers
+comments
+basic PGN information
+
+This forms the foundation for future CAN signal visualization and decoding.