package devicemesh

import (
	"fmt"
	"sort"
)

// schema.go: minimal JSON-Schema-like validator. We do NOT depend on a full
// JSON Schema implementation — the surface we use is small and stable:
//
//   - type: "object" | "string" | "number" | "integer" | "boolean" | "array"
//   - required: []string (names of fields that must be present and non-nil)
//   - properties: map[string]<sub-schema>
//   - items: <sub-schema> for arrays
//   - enum: []any — allowed scalar values
//   - additionalProperties: false (strict; default true)
//
// This is enough to catch LLM-induced typos (extra fields, wrong types) and
// gives the runtime a place to grow if we need oneOf/pattern later.

// ValidateInput checks the spec.InputSchema against the provided input map.
// Returns nil on success, a descriptive error otherwise. The error path is
// surfaced back to the LLM so it can self-correct.
func ValidateInput(spec ToolSpec, input map[string]any) error {
	if spec.InputSchema == nil {
		// No schema means "anything goes". Tools without a schema are rare
		// (mostly internal ones like memory.recall in 0144d).
		return nil
	}
	return validateValue("input", input, spec.InputSchema)
}

func validateValue(path string, value any, schema map[string]any) error {
	typ, _ := schema["type"].(string)
	if typ == "" {
		// No type declared: accept as-is.
		return nil
	}

	// nil handling: only allowed if the field is not required (handled by parent).
	if value == nil {
		return fmt.Errorf("%s: expected %s, got null", path, typ)
	}

	switch typ {
	case "object":
		obj, ok := value.(map[string]any)
		if !ok {
			return fmt.Errorf("%s: expected object, got %T", path, value)
		}
		return validateObject(path, obj, schema)
	case "array":
		arr, ok := coerceToAnySlice(value)
		if !ok {
			return fmt.Errorf("%s: expected array, got %T", path, value)
		}
		return validateArray(path, arr, schema)
	case "string":
		if _, ok := value.(string); !ok {
			return fmt.Errorf("%s: expected string, got %T", path, value)
		}
		return validateEnum(path, value, schema)
	case "integer":
		if !isInteger(value) {
			return fmt.Errorf("%s: expected integer, got %T (%v)", path, value, value)
		}
		return validateEnum(path, value, schema)
	case "number":
		if !isNumber(value) {
			return fmt.Errorf("%s: expected number, got %T", path, value)
		}
		return validateEnum(path, value, schema)
	case "boolean":
		if _, ok := value.(bool); !ok {
			return fmt.Errorf("%s: expected boolean, got %T", path, value)
		}
	default:
		return fmt.Errorf("%s: unknown schema type %q", path, typ)
	}
	return nil
}

func validateObject(path string, obj map[string]any, schema map[string]any) error {
	// Required fields must be present and non-nil.
	if reqRaw, ok := schema["required"]; ok {
		req, _ := asStringSlice(reqRaw)
		// Deterministic ordering of errors helps tests and LLM correction.
		sort.Strings(req)
		for _, name := range req {
			v, present := obj[name]
			if !present || v == nil {
				return fmt.Errorf("%s.%s: required field missing", path, name)
			}
		}
	}
	props, _ := schema["properties"].(map[string]any)

	// Strict additionalProperties: reject unknown keys when explicitly false.
	additional := true
	if ap, ok := schema["additionalProperties"]; ok {
		if b, isBool := ap.(bool); isBool {
			additional = b
		}
	}
	if !additional && props != nil {
		keys := make([]string, 0, len(obj))
		for k := range obj {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			if _, known := props[k]; !known {
				return fmt.Errorf("%s.%s: unknown field (additionalProperties=false)", path, k)
			}
		}
	}

	if props == nil {
		return nil
	}
	// Walk known properties.
	names := make([]string, 0, len(props))
	for k := range props {
		names = append(names, k)
	}
	sort.Strings(names)
	for _, name := range names {
		sub, _ := props[name].(map[string]any)
		if sub == nil {
			continue
		}
		v, present := obj[name]
		if !present {
			continue // absent + not required ⇒ ok
		}
		if v == nil {
			continue // nil + not required ⇒ ok
		}
		if err := validateValue(path+"."+name, v, sub); err != nil {
			return err
		}
	}
	return nil
}

func validateArray(path string, arr []any, schema map[string]any) error {
	itemSchema, _ := schema["items"].(map[string]any)
	if itemSchema == nil {
		return nil
	}
	for i, v := range arr {
		if err := validateValue(fmt.Sprintf("%s[%d]", path, i), v, itemSchema); err != nil {
			return err
		}
	}
	return nil
}

func validateEnum(path string, value any, schema map[string]any) error {
	enumRaw, ok := schema["enum"]
	if !ok {
		return nil
	}
	enum, _ := enumRaw.([]any)
	if len(enum) == 0 {
		return nil
	}
	for _, allowed := range enum {
		if fmt.Sprint(allowed) == fmt.Sprint(value) {
			return nil
		}
	}
	return fmt.Errorf("%s: value %v not in enum %v", path, value, enum)
}

func isInteger(v any) bool {
	switch n := v.(type) {
	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
		return true
	case float32:
		return float64(n) == float64(int64(n))
	case float64:
		return n == float64(int64(n))
	}
	return false
}

func isNumber(v any) bool {
	switch v.(type) {
	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, float32, float64:
		return true
	}
	return false
}

// coerceToAnySlice accepts []any or any typed slice ([]string, []int, ...)
// and returns it as []any. This keeps the schema validator forgiving when
// callers pass native Go slices directly (common in tests and ArgMapping
// outputs) instead of JSON-decoded []any.
func coerceToAnySlice(v any) ([]any, bool) {
	switch s := v.(type) {
	case []any:
		return s, true
	case []string:
		out := make([]any, len(s))
		for i, e := range s {
			out[i] = e
		}
		return out, true
	case []int:
		out := make([]any, len(s))
		for i, e := range s {
			out[i] = e
		}
		return out, true
	case []float64:
		out := make([]any, len(s))
		for i, e := range s {
			out[i] = e
		}
		return out, true
	}
	return nil, false
}

func asStringSlice(v any) ([]string, bool) {
	switch s := v.(type) {
	case []string:
		out := make([]string, len(s))
		copy(out, s)
		return out, true
	case []any:
		out := make([]string, 0, len(s))
		for _, e := range s {
			str, ok := e.(string)
			if !ok {
				return nil, false
			}
			out = append(out, str)
		}
		return out, true
	}
	return nil, false
}