Refactor prometheus-pusher following Go best practices

Major refactoring to improve code organization and follow Go conventions:
- Moved main entry point to cmd/prometheus-pusher/main.go
- Organized code into internal packages (config, metrics, parser, ingester, version)
- Implemented proper dependency injection (no package-level variables)
- Added context.Context to all blocking operations
- Used value semantics where feasible (Sample, Config, Ingesters)
- Proper error wrapping with %w throughout
- All functions under 50 lines, focused and single-purpose
- Consistent ordering: constants, types, constructors, public, private
- Added -version flag to display version from internal/version package

Package structure:
- cmd/prometheus-pusher: Main entry point with flag parsing and mode routing
- internal/config: Configuration types and constants
- internal/version: Version constant (0.0.0)
- internal/metrics: Sample type and Collectors for metric generation
- internal/parser: CSV/JSON parsers with context support
- internal/ingester: Pushgateway, RemoteWrite, and Auto ingesters

All modes tested and working: realtime, historic, backfill, auto

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/f3s/prometheus-pusher/internal/parser/json.go b/f3s/prometheus-pusher/internal/parser/json.go
new file mode 100644
index 0000000..b6b230c
--- /dev/null
+++ b/f3s/prometheus-pusher/internal/parser/json.go
@@ -0,0 +1,62 @@
+package parser
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"time"
+
+	"prometheus-pusher/internal/metrics"
+)
+
+// JSONParser parses metrics from JSON format
+type JSONParser struct{}
+
+// NewJSONParser creates a new JSON parser
+func NewJSONParser() *JSONParser {
+	return &JSONParser{}
+}
+
+type jsonSample struct {
+	Metric      string            `json:"metric"`
+	Labels      map[string]string `json:"labels"`
+	Value       float64           `json:"value"`
+	TimestampMs int64             `json:"timestamp_ms,omitempty"`
+}
+
+// Parse reads metrics from JSON format
+func (p *JSONParser) Parse(ctx context.Context, reader io.Reader) ([]metrics.Sample, error) {
+	var rawSamples []jsonSample
+
+	decoder := json.NewDecoder(reader)
+	if err := decoder.Decode(&rawSamples); err != nil {
+		return nil, fmt.Errorf("failed to parse JSON: %w", err)
+	}
+
+	samples := make([]metrics.Sample, 0, len(rawSamples))
+	for _, raw := range rawSamples {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
+		if raw.Metric == "" {
+			continue
+		}
+
+		timestamp := time.Now()
+		if raw.TimestampMs > 0 {
+			timestamp = time.UnixMilli(raw.TimestampMs)
+		}
+
+		if raw.Labels == nil {
+			raw.Labels = make(map[string]string)
+		}
+
+		samples = append(samples, metrics.NewSample(raw.Metric, raw.Labels, raw.Value, timestamp))
+	}
+
+	return samples, nil
+}