fix: Preserve config formatting when updating reset flag

Use line-based approach instead of YAML unmarshal/marshal to prevent
config file rewriting with zero values. This ensures monitors that omit
fields like interval and timeout continue to inherit from group defaults.

1 files changed, 53 insertions, 22 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 4d428fc..5a173b6 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -3,6 +3,7 @@ package config
 import (
 	"fmt"
 	"os"
+	"strings"
 	"time"
 
 	"gopkg.in/yaml.v3"
@@ -350,6 +351,7 @@ type MonitorWithGroup struct {
 }
 
 // UpdateResetFlag updates the reset_on_next_check flag for a specific monitor in the config file
+// Uses a line-based approach to preserve original formatting and omitted fields
 func UpdateResetFlag(configPath string, monitorName string, value bool) error {
 	// Read the config file
 	data, err := os.ReadFile(configPath)
@@ -357,38 +359,67 @@ func UpdateResetFlag(configPath string, monitorName string, value bool) error {
 		return fmt.Errorf("failed to read config file: %w", err)
 	}
 
-	// Parse as YAML
-	var cfg Config
-	if err := yaml.Unmarshal(data, &cfg); err != nil {
-		return fmt.Errorf("failed to parse config file: %w", err)
-	}
+	lines := strings.Split(string(data), "\n")
+	inMonitor := false
+	monitorIndent := ""
+	foundMonitor := false
+
+	for i := 0; i < len(lines); i++ {
+		line := lines[i]
+		trimmed := strings.TrimSpace(line)
+
+		// Check if this is the start of our target monitor
+		if strings.HasPrefix(trimmed, "- name:") || strings.HasPrefix(trimmed, "name:") {
+			// Extract monitor name from line
+			namePart := strings.TrimPrefix(trimmed, "- name:")
+			namePart = strings.TrimPrefix(namePart, "name:")
+			namePart = strings.TrimSpace(namePart)
+			namePart = strings.Trim(namePart, "\"'")
+
+			if namePart == monitorName {
+				inMonitor = true
+				foundMonitor = true
+				// Calculate the indentation level
+				monitorIndent = line[:len(line)-len(strings.TrimLeft(line, " \t"))]
+				continue
+			}
+		}
 
-	// Find and update the monitor
-	found := false
-	for i := range cfg.Groups {
-		for j := range cfg.Groups[i].Monitors {
-			if cfg.Groups[i].Monitors[j].Name == monitorName {
-				cfg.Groups[i].Monitors[j].ResetOnNextCheck = value
-				found = true
+		// If we're in the target monitor, look for reset_on_next_check or end of monitor
+		if inMonitor {
+			// Check if we've left the monitor section (new monitor or less indented line)
+			if strings.HasPrefix(trimmed, "- name:") || strings.HasPrefix(trimmed, "name:") {
+				// We've reached another monitor without finding reset_on_next_check
+				// Insert the line before this one if we're setting to false
+				if !value {
+					// Only add if setting to false (after a reset)
+					insertLine := monitorIndent + "  reset_on_next_check: false"
+					lines = append(lines[:i], append([]string{insertLine}, lines[i:]...)...)
+				}
+				break
+			}
+
+			// Check if this line is reset_on_next_check
+			if strings.Contains(trimmed, "reset_on_next_check:") {
+				// Update the value
+				if !value {
+					// Set to false after reset
+					lines[i] = monitorIndent + "  reset_on_next_check: false"
+				} else {
+					// Keep as true (should already be true, but update to be sure)
+					lines[i] = monitorIndent + "  reset_on_next_check: true"
+				}
 				break
 			}
-		}
-		if found {
-			break
 		}
 	}
 
-	if !found {
+	if !foundMonitor {
 		return fmt.Errorf("monitor %q not found in config", monitorName)
 	}
 
-	// Marshal back to YAML
-	newData, err := yaml.Marshal(&cfg)
-	if err != nil {
-		return fmt.Errorf("failed to marshal config: %w", err)
-	}
-
 	// Write back to file
+	newData := []byte(strings.Join(lines, "\n"))
 	if err := os.WriteFile(configPath, newData, 0644); err != nil {
 		return fmt.Errorf("failed to write config file: %w", err)
 	}