Enhance EML parsing function documentation

Added detailed doc comments to EML parsing functions, specifying parameters, return values, and providing thorough explanations of functionalities to improve code understandability and maintainability. This helps future developers and users comprehend the usage and behavior of these functions more effectively.

eml.go

@@ -18,13 +18,35 @@ import (
 	"strings"
 )
 
-// EMLToMsgFromString will parse a given EML string and returns a pre-filled Msg pointer.
+// EMLToMsgFromString parses a given EML string and returns a pre-filled Msg pointer.
+//
+// This function takes an EML formatted string, converts it into a bytes buffer, and then
+// calls EMLToMsgFromReader to parse the buffer and create a Msg object. This provides a
+// convenient way to convert EML strings directly into Msg objects.
+//
+// Parameters:
+//   - emlString: A string containing the EML formatted message.
+//
+// Returns:
+//   - A pointer to the Msg object populated with the parsed data, and an error if parsing
+//     fails.
 func EMLToMsgFromString(emlString string) (*Msg, error) {
 	eb := bytes.NewBufferString(emlString)
 	return EMLToMsgFromReader(eb)
 }
 
-// EMLToMsgFromReader will parse a reader that holds EML content and returns a pre-filled Msg pointer.
+// EMLToMsgFromReader parses a reader that holds EML content and returns a pre-filled Msg pointer.
+//
+// This function reads EML content from the provided io.Reader and populates a Msg object
+// with the parsed data. It initializes the Msg and extracts headers and body parts from
+// the EML content. Any errors encountered during parsing are returned.
+//
+// Parameters:
+//   - reader: An io.Reader containing the EML formatted message.
+//
+// Returns:
+//   - A pointer to the Msg object populated with the parsed data, and an error if parsing
+//     fails.
 func EMLToMsgFromReader(reader io.Reader) (*Msg, error) {
 	msg := &Msg{
 		addrHeader:    make(map[AddrHeader][]*netmail.Address),
@@ -45,7 +67,19 @@ func EMLToMsgFromReader(reader io.Reader) (*Msg, error) {
 	return msg, nil
 }
 
-// EMLToMsgFromFile will open and parse a .eml file at a provided file path and returns a pre-filled Msg pointer.
+// EMLToMsgFromFile opens and parses a .eml file at a provided file path and returns a
+// pre-filled Msg pointer.
+//
+// This function attempts to read and parse an EML file located at the specified file path.
+// It initializes a Msg object and populates it with the parsed headers and body. Any errors
+// encountered during the file operations or parsing are returned.
+//
+// Parameters:
+//   - filePath: The path to the .eml file to be parsed.
+//
+// Returns:
+//   - A pointer to the Msg object populated with the parsed data, and an error if parsing
+//     fails.
 func EMLToMsgFromFile(filePath string) (*Msg, error) {
 	msg := &Msg{
 		addrHeader:    make(map[AddrHeader][]*netmail.Address),
@@ -67,6 +101,18 @@ func EMLToMsgFromFile(filePath string) (*Msg, error) {
 }
 
 // parseEML parses the EML's headers and body and inserts the parsed values into the Msg.
+//
+// This function extracts relevant header fields and body content from the parsed EML message
+// and stores them in the provided Msg object. It handles various header types and body
+// parts, ensuring that the Msg is correctly populated with all necessary information.
+//
+// Parameters:
+//   - parsedMsg: A pointer to the netmail.Message containing the parsed EML data.
+//   - bodybuf: A bytes.Buffer containing the body content of the EML message.
+//   - msg: A pointer to the Msg object to be populated with the parsed data.
+//
+// Returns:
+//   - An error if any issues occur during the parsing process; otherwise, returns nil.
 func parseEML(parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *Msg) error {
 	if err := parseEMLHeaders(&parsedMsg.Header, msg); err != nil {
 		return fmt.Errorf("failed to parse EML headers: %w", err)
@@ -78,6 +124,17 @@ func parseEML(parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *Msg) error
 }
 
 // readEML opens an EML file and uses net/mail to parse the header and body.
+//
+// This function opens the specified EML file for reading and utilizes the net/mail package
+// to parse the message's headers and body. It returns the parsed message and a buffer
+// containing the body content, along with any errors encountered during the process.
+//
+// Parameters:
+//   - filePath: The path to the EML file to be opened and parsed.
+//
+// Returns:
+//   - A pointer to the parsed netmail.Message, a bytes.Buffer containing the body, and an
+//     error if any issues occur during file operations or parsing.
 func readEML(filePath string) (*netmail.Message, *bytes.Buffer, error) {
 	fileHandle, err := os.Open(filePath)
 	if err != nil {
@@ -90,6 +147,18 @@ func readEML(filePath string) (*netmail.Message, *bytes.Buffer, error) {
 }
 
 // readEMLFromReader uses net/mail to parse the header and body from a given io.Reader.
+//
+// This function reads the EML content from the provided io.Reader and uses the net/mail
+// package to parse the message's headers and body. It returns the parsed netmail.Message
+// along with a bytes.Buffer containing the body content. Any errors encountered during
+// the parsing process are returned.
+//
+// Parameters:
+//   - reader: An io.Reader containing the EML formatted message.
+//
+// Returns:
+//   - A pointer to the parsed netmail.Message, a bytes.Buffer containing the body, and an
+//     error if any issues occur during parsing.
 func readEMLFromReader(reader io.Reader) (*netmail.Message, *bytes.Buffer, error) {
 	parsedMsg, err := netmail.ReadMessage(reader)
 	if err != nil {
@@ -104,8 +173,18 @@ func readEMLFromReader(reader io.Reader) (*netmail.Message, *bytes.Buffer, error
 	return parsedMsg, &buf, nil
 }
 
-// parseEMLHeaders will check the EML headers for the most common headers and set the according settings
+// parseEMLHeaders parses the EML's headers and populates the Msg with relevant information.
-// in the Msg.
+//
+// This function checks the EML headers for common headers and sets the corresponding fields
+// in the Msg object. It extracts address headers, content types, and other relevant data
+// for further processing.
+//
+// Parameters:
+//   - mailHeader: A pointer to the netmail.Header containing the EML headers.
+//   - msg: A pointer to the Msg object to be populated with parsed header information.
+//
+// Returns:
+//   - An error if parsing the headers fails; otherwise, returns nil.
 func parseEMLHeaders(mailHeader *netmail.Header, msg *Msg) error {
 	commonHeaders := []Header{
 		HeaderContentType, HeaderImportance, HeaderInReplyTo, HeaderListUnsubscribe,
@@ -173,7 +252,19 @@ func parseEMLHeaders(mailHeader *netmail.Header, msg *Msg) error {
 	return nil
 }
 
-// parseEMLBodyParts parses the body of a EML based on the different content types and encodings.
+// parseEMLBodyParts parses the body of an EML based on the different content types and encodings.
+//
+// This function examines the content type of the parsed EML message and processes the body
+// parts accordingly. It handles both plain text and multipart types, ensuring that the
+// Msg object is populated with the appropriate body content.
+//
+// Parameters:
+//   - parsedMsg: A pointer to the netmail.Message containing the parsed EML data.
+//   - bodybuf: A bytes.Buffer containing the body content of the EML message.
+//   - msg: A pointer to the Msg object to be populated with the parsed body content.
+//
+// Returns:
+//   - An error if any issues occur during the body parsing process; otherwise, returns nil.
 func parseEMLBodyParts(parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *Msg) error {
 	// Extract the transfer encoding of the body
 	mediatype, params, err := mime.ParseMediaType(parsedMsg.Header.Get(HeaderContentType.String()))
@@ -210,7 +301,20 @@ func parseEMLBodyParts(parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *M
 	return nil
 }
 
-// parseEMLBodyPlain parses the mail body of plain type mails.
+// parseEMLBodyPlain parses the mail body of plain type messages.
+//
+// This function handles the parsing of plain text messages based on their encoding. It
+// identifies the content transfer encoding and decodes the body content accordingly,
+// storing the result in the provided Msg object.
+//
+// Parameters:
+//   - mediatype: The media type of the message (e.g., text/plain).
+//   - parsedMsg: A pointer to the netmail.Message containing the parsed EML data.
+//   - bodybuf: A bytes.Buffer containing the body content of the EML message.
+//   - msg: A pointer to the Msg object to be populated with the parsed body content.
+//
+// Returns:
+//   - An error if any issues occur during the parsing of the plain body; otherwise, returns nil.
 func parseEMLBodyPlain(mediatype string, parsedMsg *netmail.Message, bodybuf *bytes.Buffer, msg *Msg) error {
 	contentTransferEnc := parsedMsg.Header.Get(HeaderContentTransferEnc.String())
 	// If no Content-Transfer-Encoding is set, we can imply 7bit US-ASCII encoding
@@ -248,7 +352,20 @@ func parseEMLBodyPlain(mediatype string, parsedMsg *netmail.Message, bodybuf *by
 	return fmt.Errorf("unsupported Content-Transfer-Encoding")
 }
 
-// parseEMLMultipart parses a multipart body part of a EML
+// parseEMLMultipart parses a multipart body part of an EML message.
+//
+// This function handles the parsing of multipart messages, extracting the individual parts
+// and determining their content types. It processes each part according to its content type
+// and ensures that all relevant data is stored in the Msg object.
+//
+// Parameters:
+//   - params: A map containing the parameters from the multipart content type.
+//   - bodybuf: A bytes.Buffer containing the body content of the EML message.
+//   - msg: A pointer to the Msg object to be populated with the parsed body parts.
+//
+// Returns:
+//   - An error if any issues occur during the parsing of the multipart body; otherwise,
+//     returns nil.
 func parseEMLMultipart(params map[string]string, bodybuf *bytes.Buffer, msg *Msg) error {
 	boundary, ok := params["boundary"]
 	if !ok {
@@ -349,6 +466,14 @@ ReadNextPart:
 }
 
 // parseEMLEncoding parses and determines the encoding of the message.
+//
+// This function extracts the content transfer encoding from the EML headers and sets the
+// corresponding encoding in the Msg object. It ensures that the correct encoding is used
+// for further processing of the message content.
+//
+// Parameters:
+//   - mailHeader: A pointer to the netmail.Header containing the EML headers.
+//   - msg: A pointer to the Msg object to be updated with the encoding information.
 func parseEMLEncoding(mailHeader *netmail.Header, msg *Msg) {
 	if value := mailHeader.Get(HeaderContentTransferEnc.String()); value != "" {
 		switch {
@@ -363,6 +488,14 @@ func parseEMLEncoding(mailHeader *netmail.Header, msg *Msg) {
 }
 
 // parseEMLContentTypeCharset parses and determines the charset and content type of the message.
+//
+// This function extracts the content type and charset from the EML headers, setting them
+// appropriately in the Msg object. It ensures that the Msg object is configured with the
+// correct content type for further processing.
+//
+// Parameters:
+//   - mailHeader: A pointer to the netmail.Header containing the EML headers.
+//   - msg: A pointer to the Msg object to be updated with content type and charset information.
 func parseEMLContentTypeCharset(mailHeader *netmail.Header, msg *Msg) {
 	if value := mailHeader.Get(HeaderContentType.String()); value != "" {
 		contentType, optional := parseMultiPartHeader(value)
@@ -377,6 +510,17 @@ func parseEMLContentTypeCharset(mailHeader *netmail.Header, msg *Msg) {
 }
 
 // handleEMLMultiPartBase64Encoding sets the content body of a base64 encoded Part.
+//
+// This function decodes the base64 encoded content of a multipart part and stores the
+// resulting content in the provided Part object. It handles any errors that occur during
+// the decoding process.
+//
+// Parameters:
+//   - multiPartData: A byte slice containing the base64 encoded data.
+//   - part: A pointer to the Part object where the decoded content will be stored.
+//
+// Returns:
+//   - An error if the base64 decoding fails; otherwise, returns nil.
 func handleEMLMultiPartBase64Encoding(multiPartData []byte, part *Part) error {
 	part.SetEncoding(EncodingB64)
 	content, err := base64.StdEncoding.DecodeString(string(multiPartData))
@@ -387,7 +531,17 @@ func handleEMLMultiPartBase64Encoding(multiPartData []byte, part *Part) error {
 	return nil
 }
 
-// parseMultiPartHeader parses a multipart header and returns the value and optional parts as separate map.
+// parseMultiPartHeader parses a multipart header and returns the value and optional parts as a map.
+//
+// This function splits a multipart header into its main value and any optional parameters,
+// returning them separately. It helps in processing multipart messages by extracting
+// relevant information from headers.
+//
+// Parameters:
+//   - multiPartHeader: A string representing the multipart header to be parsed.
+//
+// Returns:
+//   - The main header value as a string and a map of optional parameters.
 func parseMultiPartHeader(multiPartHeader string) (header string, optional map[string]string) {
 	optional = make(map[string]string)
 	headerSplit := strings.SplitN(multiPartHeader, ";", 2)
@@ -403,6 +557,19 @@ func parseMultiPartHeader(multiPartHeader string) (header string, optional map[s
 }
 
 // parseEMLAttachmentEmbed parses a multipart that is an attachment or embed.
+//
+// This function handles the parsing of multipart sections that are marked as attachments or
+// embedded content. It processes the content disposition and sets the appropriate fields in
+// the Msg object based on the parsed data.
+//
+// Parameters:
+//   - contentDisposition: A slice of strings containing the content disposition header.
+//   - multiPart: A pointer to the multipart.Part to be parsed.
+//   - msg: A pointer to the Msg object to be populated with the attachment or embed data.
+//
+// Returns:
+//   - An error if any issues occur during the parsing of attachments or embeds; otherwise,
+//     returns nil.
 func parseEMLAttachmentEmbed(contentDisposition []string, multiPart *multipart.Part, msg *Msg) error {
 	cdType, optional := parseMultiPartHeader(contentDisposition[0])
 	filename := "generic.attachment"