package registry

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

// IndexResult holds stats from an indexing run.
type IndexResult struct {
	Functions        int
	Types            int
	ValidationErrors []string
	Errors           []string
}

// Index walks the registry root, parses all .md files, validates integrity,
// and populates the database. It uses two passes:
// 1. Parse all entries and collect known IDs
// 2. Validate references against known IDs, then insert valid entries
func Index(db *DB, root string) (*IndexResult, error) {
	if err := db.Purge(); err != nil {
		return nil, fmt.Errorf("purging database: %w", err)
	}

	result := &IndexResult{}

	// Pass 1: parse everything
	var functions []*Function
	var types []*Type

	functionsDir := filepath.Join(root, "functions")
	if _, err := os.Stat(functionsDir); err == nil {
		filepath.Walk(functionsDir, func(path string, info os.FileInfo, err error) error {
			if err != nil || info.IsDir() || !strings.HasSuffix(path, ".md") {
				return nil
			}
			f, err := ParseFunctionMD(path)
			if err != nil {
				result.Errors = append(result.Errors, fmt.Sprintf("parse %s: %v", path, err))
				return nil
			}
			functions = append(functions, f)
			return nil
		})
	}

	typesDir := filepath.Join(root, "types")
	if _, err := os.Stat(typesDir); err == nil {
		filepath.Walk(typesDir, func(path string, info os.FileInfo, err error) error {
			if err != nil || info.IsDir() || !strings.HasSuffix(path, ".md") {
				return nil
			}
			t, err := ParseTypeMD(path)
			if err != nil {
				result.Errors = append(result.Errors, fmt.Sprintf("parse %s: %v", path, err))
				return nil
			}
			types = append(types, t)
			return nil
		})
	}

	// Build known ID sets
	knownFunctions := make(map[string]bool, len(functions))
	for _, f := range functions {
		knownFunctions[f.ID] = true
	}
	knownTypes := make(map[string]bool, len(types))
	for _, t := range types {
		knownTypes[t.ID] = true
	}

	// Pass 2: validate and insert
	for _, t := range types {
		if verr := ValidateType(t, knownTypes); verr != nil {
			result.ValidationErrors = append(result.ValidationErrors, verr.Error())
			continue
		}
		if err := db.InsertType(t); err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("insert %s: %v", t.ID, err))
			continue
		}
		result.Types++
	}

	for _, f := range functions {
		if verr := ValidateFunction(f, knownFunctions, knownTypes); verr != nil {
			result.ValidationErrors = append(result.ValidationErrors, verr.Error())
			continue
		}
		if err := db.InsertFunction(f); err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("insert %s: %v", f.ID, err))
			continue
		}
		result.Functions++
	}

	return result, nil
}