package tool

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"sync"

	"github.com/santhosh-tekuri/jsonschema/v5"
)

// quotedRe extracts single-quoted tokens, e.g. the property names inside the
// library's required error message "missing properties: 'a', 'b'".
var quotedRe = regexp.MustCompile(`'([^']+)'`)

// schemaCache reuses compiled schemas keyed by their canonical JSON bytes.
// Tool.Parameters is called on every dispatch, so recompiling each round is
// wasteful; the map is concurrency-safe so concurrent dispatches share entries.
var schemaCache sync.Map // key: string (schema JSON), value: *jsonschema.Schema

// validateArgs validates args against the tool's JSON Schema. It first applies
// schema "default" values for absent properties (mirroring MCP applySchema and
// OpenClaw's Convert), then coerces model-emitted scalar strings into the types
// the schema asks for (OpenClaw coerceWithJsonSchema), then runs a full
// santhosh-tekuri/jsonschema validation supporting required, properties, nested
// objects, array items, additionalProperties, allOf/anyOf/oneOf, type unions,
// enum, min/max and pattern. Validation failures carry the offending instance
// location (e.g. /count) so the caller and front-end can pinpoint the argument.
//
// The args map is mutated in place: defaults are inserted and values are coerced
// so the tool subsequently receives the arguments it declared.
func validateArgs(schema map[string]any, args map[string]any) error {
	if schema == nil {
		return nil
	}
	if args == nil {
		args = map[string]any{}
	}

	compiled, err := compileSchema(schema)
	if err != nil {
		return fmt.Errorf("schema: %w", err)
	}

	applyDefaults(schema, args)
	coerceWithSchema(args, schema)

	if verr := compiled.Validate(args); verr != nil {
		return newValidationError(verr)
	}
	return nil
}

// compileSchema compiles schema (or returns a cached compiled schema) using
// draft-7 semantics for schemas that do not declare "$schema", since tool input
// schemas are overwhelmingly OpenAI-function-shaped (tuple "items" arrays
// included). Schemas that declare their own "$schema" are honored as-is.
func compileSchema(schema map[string]any) (*jsonschema.Schema, error) {
	raw, err := json.Marshal(schema)
	if err != nil {
		return nil, fmt.Errorf("schema is not json-marshalable: %w", err)
	}
	key := string(raw)
	if cached, ok := schemaCache.Load(key); ok {
		return cached.(*jsonschema.Schema), nil
	}

	c := jsonschema.NewCompiler()
	c.Draft = jsonschema.Draft7
	if err := c.AddResource("tool-schema.json", bytes.NewReader(raw)); err != nil {
		return nil, err
	}
	sch, err := c.Compile("tool-schema.json")
	if err != nil {
		return nil, err
	}
	actual, _ := schemaCache.LoadOrStore(key, sch)
	return actual.(*jsonschema.Schema), nil
}

// newValidationError renders a *jsonschema.ValidationError into a compact,
// human-readable report of the leaf failures, each carrying the instance
// location (e.g. /count or /user/age) so callers can locate the exact property.
func newValidationError(err error) error {
	var ve *jsonschema.ValidationError
	if !errors.As(err, &ve) {
		return err
	}
	var sb strings.Builder
	for _, e := range flattenLeaves(ve) {
		if sb.Len() > 0 {
			sb.WriteString("; ")
		}
		sb.WriteString(formatErrorPath(e))
		sb.WriteString(": ")
		sb.WriteString(e.Message)
	}
	if sb.Len() == 0 {
		return err
	}
	return errors.New(sb.String())
}

// flattenLeaves walks the ValidationError tree skipping the root wrapper
// ("doesn't validate with ...") and returning every sub-error that carries its
// own message.
func flattenLeaves(ve *jsonschema.ValidationError) []*jsonschema.ValidationError {
	var leaves []*jsonschema.ValidationError
	var walk func(*jsonschema.ValidationError)
	walk = func(e *jsonschema.ValidationError) {
		if e.Message != "" && !strings.HasPrefix(e.Message, "doesn't validate with") {
			leaves = append(leaves, e)
		}
		for _, c := range e.Causes {
			walk(c)
		}
	}
	for _, c := range ve.Causes {
		walk(c)
	}
	return leaves
}

// formatErrorPath renders the instance location for a leaf error as a JSON
// pointer (e.g. /count). For a missing-required error the instance location
// points at the enclosing object, so the first missing property name is
// appended to give a precise path.
func formatErrorPath(e *jsonschema.ValidationError) string {
	if e.KeywordLocation == "required" || strings.HasSuffix(e.KeywordLocation, "/required") {
		if names := quotedTokens(e.Message); len(names) > 0 {
			return strings.TrimRight(e.InstanceLocation, "/") + "/" + names[0]
		}
	}
	if e.InstanceLocation == "" {
		return "/"
	}
	return e.InstanceLocation
}

// quotedTokens extracts every single-quoted token from s.
func quotedTokens(s string) []string {
	matches := quotedRe.FindAllStringSubmatch(s, -1)
	out := make([]string, 0, len(matches))
	for _, m := range matches {
		out = append(out, m[1])
	}
	return out
}