refactor: reorganize code into proper package structure

- Move main.go to cmd/ai-podcast directory following Go conventions
- Consolidate packages to avoid fragmentation:
  - internal/content: combines article fetching and text processing
  - internal/audio: audio processing functionality
  - internal/ai: OpenAI integration
- Move all test files to their respective packages
- Export necessary constants and functions for cross-package usage
- Generate package-specific mocks in each package's mocks directory
- Update all imports to reflect new package structure
- Fix import shadowing and other linting issues

All tests pass with race detection enabled and no linting issues remain.

Author: umputun

main.go cmd/ai-podcast/main.gomain.go renamed to cmd/ai-podcast/main.go

@@ -8,6 +8,9 @@ import (
 	"sync"
 	"time"
 
+	"github.com/radio-t/ai-podcast/internal/ai"
+	"github.com/radio-t/ai-podcast/internal/audio"
+	"github.com/radio-t/ai-podcast/internal/content"
 	"github.com/radio-t/ai-podcast/podcast"
 )
 
@@ -102,9 +105,9 @@ func main() {
 
 func run(config podcast.Config) error {
 	// create services
-	articleFetcher := NewHTTPArticleFetcher(nil)
-	openAI := NewOpenAIService(config.OpenAIAPIKey, nil)
-	audioProcessor := NewFFmpegAudioProcessor()
+	articleFetcher := content.NewHTTPArticleFetcher(nil)
+	openAI := ai.NewOpenAIService(config.OpenAIAPIKey, nil)
+	audioProcessor := audio.NewFFmpegAudioProcessor()
 
 	return runWithDependencies(config, articleFetcher, openAI, audioProcessor)
 }
@@ -156,7 +159,7 @@ func runWithDependencies(config podcast.Config, articleFetcher ArticleFetcher, o
 // generateAndStreamToIcecast generates speech for each message and streams to Icecast
 func generateAndStreamToIcecast(params podcast.GenerateAndStreamParams, openAI OpenAIClient, audioProcessor AudioProcessor) error {
 	// create text processor
-	textProcessor := NewTextProcessor()
+	textProcessor := content.NewTextProcessor()
 
 	// map host names to their gender and voice
 	hostMap := podcast.CreateHostMap(params.Config.Hosts)
@@ -190,9 +193,9 @@ func generateAndStreamToIcecast(params podcast.GenerateAndStreamParams, openAI O
 	}
 
 	// create concat file for ffmpeg
-	concatFile, err := createConcatFile(tempDir, audioFiles)
+	concatFile, err := audio.CreateConcatFile(tempDir, audioFiles)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to create concat file: %w", err)
 	}
 
 	// stream to Icecast
@@ -260,7 +263,7 @@ func generateAndPlayLocally(params podcast.GenerateAndStreamParams, openAI OpenA
 	stopChan := make(chan struct{})
 
 	// create a buffer for pre-generated segments
-	segmentBuffer := make([]podcast.SpeechSegment, 0, preGeneratedSegmentsBuffer)
+	segmentBuffer := make([]podcast.SpeechSegment, 0, content.PreGeneratedSegmentsBuffer)
 	bufferMutex := sync.Mutex{}
 
 	// start background worker for speech generation
@@ -275,7 +278,7 @@ func generateAndPlayLocally(params podcast.GenerateAndStreamParams, openAI OpenA
 	// start pre-generating segments
 	fmt.Println("Starting pre-generation of segments...")
 	currentIndex := 0
-	for i := 0; i < preGeneratedSegmentsBuffer && currentIndex < len(params.Discussion.Messages); i++ {
+	for i := 0; i < content.PreGeneratedSegmentsBuffer && currentIndex < len(params.Discussion.Messages); i++ {
 		msg := params.Discussion.Messages[currentIndex]
 		reqParams := podcast.CreateSpeechRequestParams{
 			Msg:     msg,
@@ -389,7 +392,7 @@ func processSegments(params podcast.ProcessSegmentsParams, audioProcessor AudioP
 		select {
 		case segment = <-params.ResultChan:
 			fmt.Printf("Received segment %d from %s\n", segment.Index, segment.Host)
-		case <-time.After(speechGenerationTimeout):
+		case <-time.After(content.SpeechGenerationTimeout):
 			fmt.Println("Timeout waiting for speech generation!")
 			return nil, fmt.Errorf("timeout waiting for speech generation")
 		}
@@ -474,9 +477,10 @@ func processOrderedSegment(params podcast.ProcessOrderedSegmentParams, audioProc
 
 // playSegment plays a single audio segment
 func playSegment(params podcast.PlaySegmentParams, audioProcessor AudioProcessor) error {
+	textProcessor := content.NewTextProcessor()
 	playStartTime := time.Now()
 	fmt.Printf("\nPlaying audio from %s (message %d)...\n", params.Segment.Host, params.Index+1)
-	fmt.Printf("Text: %s\n", truncateString(params.Segment.Msg.Content, displayTruncateLength))
+	fmt.Printf("Text: %s\n", textProcessor.TruncateString(params.Segment.Msg.Content, content.DisplayTruncateLength))
 
 	err := audioProcessor.Play(params.Filename)
 	if err != nil {

main_test.go cmd/ai-podcast/main_test.gomain_test.go renamed to cmd/ai-podcast/main_test.go

@@ -7,7 +7,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"github.com/radio-t/ai-podcast/mocks"
+	"github.com/radio-t/ai-podcast/cmd/ai-podcast/mocks"
 	"github.com/radio-t/ai-podcast/podcast"
 )
 
@@ -61,14 +61,6 @@ func TestCreateSpeechRequest(t *testing.T) {
 	}
 }
 
-func TestNewOpenAIService(t *testing.T) {
-	t.Run("with nil http client", func(t *testing.T) {
-		service := NewOpenAIService("test-key", nil)
-		assert.Equal(t, "test-key", service.apiKey)
-		assert.NotNil(t, service.httpClient)
-	})
-}
-
 // Test using generated mocks
 func TestGenerateAndStreamWithMocks(t *testing.T) {
 	mockOpenAI := &mocks.OpenAIClientMock{}
@@ -146,16 +138,6 @@ func TestGenerateAndStreamWithMocks(t *testing.T) {
 	assert.Len(t, mockArticle.FetchCalls(), 1)
 }
 
-func TestNewFFmpegAudioProcessor(t *testing.T) {
-	processor := NewFFmpegAudioProcessor()
-	assert.NotNil(t, processor)
-}
-
-func TestNewHTTPArticleFetcher(t *testing.T) {
-	fetcher := NewHTTPArticleFetcher(nil)
-	assert.NotNil(t, fetcher)
-}
-
 func TestRunWithDependencies(t *testing.T) {
 	tests := []struct {
 		name          string

mocks/article_fetcher.go cmd/ai-podcast/mocks/article_fetcher.gomocks/article_fetcher.go renamed to cmd/ai-podcast/mocks/article_fetcher.go

@@ -1,4 +1,4 @@
-package main
+package ai
 
 import (
 	"bytes"
@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/radio-t/ai-podcast/internal/content"
 	"github.com/radio-t/ai-podcast/podcast"
 )
 
@@ -28,7 +29,7 @@ type OpenAIService struct {
 // NewOpenAIService creates a new OpenAI service
 func NewOpenAIService(apiKey string, httpClient HTTPClient) *OpenAIService {
 	if httpClient == nil {
-		httpClient = &http.Client{Timeout: openAIHTTPTimeout}
+		httpClient = &http.Client{Timeout: content.OpenAIHTTPTimeout}
 	}
 	return &OpenAIService{
 		apiKey:     apiKey,
@@ -65,7 +66,7 @@ type OpenAITTSRequest struct {
 // GenerateDiscussion uses OpenAI API to create a discussion between hosts
 func (s *OpenAIService) GenerateDiscussion(params podcast.GenerateDiscussionParams) (podcast.Discussion, error) {
 	// calculate target number of messages based on duration
-	targetMessages := params.TargetDuration * messagesPerMinute
+	targetMessages := params.TargetDuration * content.MessagesPerMinute
 
 	// create the system prompt
 	systemPrompt := s.createDiscussionPrompt(params.Hosts, targetMessages, params.TargetDuration)
@@ -81,18 +82,18 @@ func (s *OpenAIService) GenerateDiscussion(params podcast.GenerateDiscussionPara
 					params.Title, params.ArticleText),
 			},
 		},
-		Temperature: openAITemperature,
-		MaxTokens:   openAIMaxTokens,
+		Temperature: content.OpenAITemperature,
+		MaxTokens:   content.OpenAIMaxTokens,
 	}
 
 	// call the OpenAI API
-	content, err := s.callChatAPI(request)
+	responseContent, err := s.callChatAPI(request)
 	if err != nil {
 		return podcast.Discussion{}, fmt.Errorf("failed to generate discussion: %w", err)
 	}
 
 	// extract and parse the JSON response
-	messages, err := s.extractMessages(content)
+	messages, err := s.extractMessages(responseContent)
 	if err != nil {
 		return podcast.Discussion{}, fmt.Errorf("failed to parse discussion: %w", err)
 	}
@@ -259,7 +260,7 @@ Start with a brief introduction of the article topic before jumping into the hea
 
 Make it feel like a real tech podcast discussion with passionate experts who aren't afraid to get heated and use strong language when they disagree.`
 
-	return fmt.Sprintf(basePrompt, hostDescriptions, targetMessages, messagesPerMinute, targetDuration)
+	return fmt.Sprintf(basePrompt, hostDescriptions, targetMessages, content.MessagesPerMinute, targetDuration)
 }
 
 // prepareHostDescriptions formats host information for the prompt
@@ -273,32 +274,32 @@ func (s *OpenAIService) prepareHostDescriptions(hosts []podcast.Host) string {
 }
 
 // extractMessages extracts and parses messages from the OpenAI response
-func (s *OpenAIService) extractMessages(content string) ([]podcast.Message, error) {
+func (s *OpenAIService) extractMessages(responseContent string) ([]podcast.Message, error) {
 	// the LLM may wrap the JSON in backticks or code block, so remove those
-	content = strings.TrimSpace(content)
-	if strings.HasPrefix(content, "```json") {
-		content = strings.TrimPrefix(content, "```json")
-		content = strings.TrimSuffix(content, "```")
-	} else if strings.HasPrefix(content, "```") {
-		content = strings.TrimPrefix(content, "```")
-		content = strings.TrimSuffix(content, "```")
+	responseContent = strings.TrimSpace(responseContent)
+	if strings.HasPrefix(responseContent, "```json") {
+		responseContent = strings.TrimPrefix(responseContent, "```json")
+		responseContent = strings.TrimSuffix(responseContent, "```")
+	} else if strings.HasPrefix(responseContent, "```") {
+		responseContent = strings.TrimPrefix(responseContent, "```")
+		responseContent = strings.TrimSuffix(responseContent, "```")
 	}
-	content = strings.TrimSpace(content)
+	responseContent = strings.TrimSpace(responseContent)
 
 	// parse the JSON into our structure
 	var rawMessages []struct {
 		Host    string `json:"host"`
 		Content string `json:"content"`
 	}
 
-	err := json.Unmarshal([]byte(content), &rawMessages)
+	err := json.Unmarshal([]byte(responseContent), &rawMessages)
 	if err != nil {
 		// if unmarshaling fails, try to extract JSON from the text
-		startIdx := strings.Index(content, "[")
-		endIdx := strings.LastIndex(content, "]")
+		startIdx := strings.Index(responseContent, "[")
+		endIdx := strings.LastIndex(responseContent, "]")
 		if startIdx >= 0 && endIdx > startIdx {
-			content = content[startIdx : endIdx+1]
-			err = json.Unmarshal([]byte(content), &rawMessages)
+			responseContent = responseContent[startIdx : endIdx+1]
+			err = json.Unmarshal([]byte(responseContent), &rawMessages)
 		}
 
 		if err != nil {

mocks/audio_processor.go cmd/ai-podcast/mocks/audio_processor.gomocks/audio_processor.go renamed to cmd/ai-podcast/mocks/audio_processor.go

@@ -1,4 +1,4 @@
-package main
+package ai
 
 import (
 	"bytes"
@@ -11,7 +11,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/radio-t/ai-podcast/mocks"
+	"github.com/radio-t/ai-podcast/internal/ai/mocks"
 	"github.com/radio-t/ai-podcast/podcast"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"