proxy: unify filtering for local models and peers

This unifies the filtering capabilities for models and peers

- stripParams: removes params in the request
- setParams: sets params in the request

fixes #453

proxy/config/filters.go

@@ -0,0 +1,81 @@
+package config
+
+import (
+	"slices"
+	"sort"
+	"strings"
+)
+
+// ProtectedParams is a list of parameters that cannot be set or stripped via filters
+// These are protected to prevent breaking the proxy's ability to route requests correctly
+var ProtectedParams = []string{"model"}
+
+// Filters contains filter settings for modifying request parameters
+// Used by both models and peers
+type Filters struct {
+	// StripParams is a comma-separated list of parameters to remove from requests
+	// The "model" parameter can never be removed
+	StripParams string `yaml:"stripParams"`
+
+	// SetParams is a dictionary of parameters to set/override in requests
+	// Protected params (like "model") cannot be set
+	SetParams map[string]any `yaml:"setParams"`
+}
+
+// SanitizedStripParams returns a sorted list of parameters to strip,
+// with duplicates, empty strings, and protected params removed
+func (f Filters) SanitizedStripParams() []string {
+	if f.StripParams == "" {
+		return nil
+	}
+
+	params := strings.Split(f.StripParams, ",")
+	cleaned := make([]string, 0, len(params))
+	seen := make(map[string]bool)
+
+	for _, param := range params {
+		trimmed := strings.TrimSpace(param)
+		// Skip protected params, empty strings, and duplicates
+		if slices.Contains(ProtectedParams, trimmed) || trimmed == "" || seen[trimmed] {
+			continue
+		}
+		seen[trimmed] = true
+		cleaned = append(cleaned, trimmed)
+	}
+
+	if len(cleaned) == 0 {
+		return nil
+	}
+
+	slices.Sort(cleaned)
+	return cleaned
+}
+
+// SanitizedSetParams returns a copy of SetParams with protected params removed
+// and keys sorted for consistent iteration order
+func (f Filters) SanitizedSetParams() (map[string]any, []string) {
+	if len(f.SetParams) == 0 {
+		return nil, nil
+	}
+
+	result := make(map[string]any, len(f.SetParams))
+	keys := make([]string, 0, len(f.SetParams))
+
+	for key, value := range f.SetParams {
+		// Skip protected params
+		if slices.Contains(ProtectedParams, key) {
+			continue
+		}
+		result[key] = value
+		keys = append(keys, key)
+	}
+
+	// Sort keys for consistent ordering
+	sort.Strings(keys)
+
+	if len(result) == 0 {
+		return nil, nil
+	}
+
+	return result, keys
+}