package main

import (
	"bufio"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"gopkg.in/yaml.v3"
)

// SafetyRules represents the safety-rules.yml schema for a plugin.
type SafetyRules struct {
	Segmentation *SegmentationRules `yaml:"segmentation"`
}

// SegmentationRules defines cross-plugin isolation constraints.
type SegmentationRules struct {
	NoGoImportsFrom       []string `yaml:"no_go_imports_from"`
	NoFrontendImportsFrom []string `yaml:"no_frontend_imports_from"`
	MigrationTablePrefix  string   `yaml:"migration_table_prefix"`
	RequireFiles          []string `yaml:"require_files"`
	FederationName        string   `yaml:"federation_name"`
}

type segmentationViolation struct {
	pluginName string
	rule       string
	file       string
	line       int
	detail     string
}

// loadSafetyRules reads safety-rules.yml from a plugin root. Returns nil if the file does not exist.
func loadSafetyRules(pluginRoot string) (*SafetyRules, error) {
	path := filepath.Join(pluginRoot, "safety-rules.yml")
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("read %s: %w", path, err)
	}
	var rules SafetyRules
	if err := yaml.Unmarshal(data, &rules); err != nil {
		return nil, fmt.Errorf("parse %s: %w", path, err)
	}
	return &rules, nil
}

// checkSegmentation runs all segmentation rules for a plugin and returns violations.
func checkSegmentation(pluginRoot, pluginName string, rules *SegmentationRules) []segmentationViolation {
	var violations []segmentationViolation

	// Rule: no_go_imports_from
	if len(rules.NoGoImportsFrom) > 0 {
		violations = append(violations, checkNoGoImports(pluginRoot, pluginName, rules.NoGoImportsFrom)...)
	}

	// Rule: no_frontend_imports_from
	if len(rules.NoFrontendImportsFrom) > 0 {
		violations = append(violations, checkNoFrontendImports(pluginRoot, pluginName, rules.NoFrontendImportsFrom)...)
	}

	// Rule: migration_table_prefix
	if rules.MigrationTablePrefix != "" {
		violations = append(violations, checkMigrationFKs(pluginRoot, pluginName, rules.MigrationTablePrefix)...)
	}

	// Rule: require_files
	for _, reqFile := range rules.RequireFiles {
		fullPath := filepath.Join(pluginRoot, reqFile)
		if !fileExists(fullPath) {
			violations = append(violations, segmentationViolation{
				pluginName: pluginName,
				rule:       "require_files",
				file:       reqFile,
				detail:     fmt.Sprintf("required file %s does not exist", reqFile),
			})
		}
	}

	// Rule: federation_name
	if rules.FederationName != "" {
		violations = append(violations, checkFederationName(pluginRoot, pluginName, rules.FederationName)...)
	}

	return violations
}

// checkNoGoImports scans Go source files for references to forbidden plugin names.
func checkNoGoImports(pluginRoot, pluginName string, forbidden []string) []segmentationViolation {
	var violations []segmentationViolation

	_ = filepath.Walk(pluginRoot, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return nil
		}
		// Skip non-Go, test files, vendor, .git, web directory
		if info.IsDir() {
			base := filepath.Base(path)
			if base == ".git" || base == ".worktrees" || base == "vendor" || base == "web" || base == "node_modules" {
				return filepath.SkipDir
			}
			return nil
		}
		if !strings.HasSuffix(path, ".go") || strings.HasSuffix(path, "_test.go") {
			return nil
		}

		rel, _ := filepath.Rel(pluginRoot, path)
		f, openErr := os.Open(path)
		if openErr != nil {
			return nil
		}
		defer func() { _ = f.Close() }()

		scanner := bufio.NewScanner(f)
		lineNum := 0
		for scanner.Scan() {
			lineNum++
			line := scanner.Text()
			for _, name := range forbidden {
				if strings.Contains(line, name) {
					violations = append(violations, segmentationViolation{
						pluginName: pluginName,
						rule:       "no_go_imports_from",
						file:       rel,
						line:       lineNum,
						detail:     fmt.Sprintf("references forbidden plugin %q", name),
					})
				}
			}
		}
		return nil
	})

	return violations
}

// checkNoFrontendImports scans TS/TSX files for references to forbidden plugin names.
func checkNoFrontendImports(pluginRoot, pluginName string, forbidden []string) []segmentationViolation {
	var violations []segmentationViolation

	webDir := filepath.Join(pluginRoot, "web")
	if !dirExists(webDir) {
		return nil
	}

	_ = filepath.Walk(webDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return nil
		}
		if info.IsDir() {
			base := filepath.Base(path)
			if base == "node_modules" || base == "dist" || base == ".git" || base == ".worktrees" {
				return filepath.SkipDir
			}
			return nil
		}
		if !strings.HasSuffix(path, ".ts") && !strings.HasSuffix(path, ".tsx") {
			return nil
		}
		// Skip generated files
		if strings.Contains(path, "/generated/") {
			return nil
		}

		rel, _ := filepath.Rel(pluginRoot, path)
		f, openErr := os.Open(path)
		if openErr != nil {
			return nil
		}
		defer func() { _ = f.Close() }()

		scanner := bufio.NewScanner(f)
		lineNum := 0
		for scanner.Scan() {
			lineNum++
			line := scanner.Text()
			for _, name := range forbidden {
				if strings.Contains(line, name) {
					violations = append(violations, segmentationViolation{
						pluginName: pluginName,
						rule:       "no_frontend_imports_from",
						file:       rel,
						line:       lineNum,
						detail:     fmt.Sprintf("references forbidden plugin %q", name),
					})
				}
			}
		}
		return nil
	})

	return violations
}

// checkMigrationFKs scans migration SQL for REFERENCES to tables outside the allowed prefix.
func checkMigrationFKs(pluginRoot, pluginName, tablePrefix string) []segmentationViolation {
	var violations []segmentationViolation

	migrationsDir := filepath.Join(pluginRoot, "migrations")
	if !dirExists(migrationsDir) {
		return nil
	}

	// Match REFERENCES <table_name>
	refRe := regexp.MustCompile(`(?i)REFERENCES\s+(\w+)`)

	_ = filepath.Walk(migrationsDir, func(path string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() || !strings.HasSuffix(path, ".sql") {
			return nil
		}
		// Skip down migrations
		if strings.Contains(filepath.Base(path), "_down") {
			return nil
		}

		rel, _ := filepath.Rel(pluginRoot, path)
		f, openErr := os.Open(path)
		if openErr != nil {
			return nil
		}
		defer func() { _ = f.Close() }()

		scanner := bufio.NewScanner(f)
		lineNum := 0
		for scanner.Scan() {
			lineNum++
			line := scanner.Text()
			// Skip down-migration blocks
			trimmed := strings.TrimSpace(line)
			if strings.HasPrefix(trimmed, "--") {
				continue
			}
			matches := refRe.FindAllStringSubmatch(line, -1)
			for _, match := range matches {
				tableName := match[1]
				// Allow references to own tables and public_users (common cross-reference)
				if strings.HasPrefix(tableName, tablePrefix) || tableName == "public_users" {
					continue
				}
				violations = append(violations, segmentationViolation{
					pluginName: pluginName,
					rule:       "migration_table_prefix",
					file:       rel,
					line:       lineNum,
					detail:     fmt.Sprintf("FK references table %q which does not have prefix %q", tableName, tablePrefix),
				})
			}
		}
		return nil
	})

	return violations
}

// checkFederationName verifies the vite.config.ts federation name matches the expected value.
func checkFederationName(pluginRoot, pluginName, expectedName string) []segmentationViolation {
	viteConfig := filepath.Join(pluginRoot, "web", "vite.config.ts")
	if !fileExists(viteConfig) {
		return nil // require_files check handles missing vite config
	}

	data, err := os.ReadFile(viteConfig)
	if err != nil {
		return nil
	}

	// Look for name: "messenger" or name: 'messenger' in federation config
	nameRe := regexp.MustCompile(`name:\s*["'](\w+)["']`)
	matches := nameRe.FindSubmatch(data)
	if len(matches) < 2 {
		return []segmentationViolation{{
			pluginName: pluginName,
			rule:       "federation_name",
			file:       "web/vite.config.ts",
			detail:     "could not find federation name declaration",
		}}
	}

	actualName := string(matches[1])
	if actualName != expectedName {
		return []segmentationViolation{{
			pluginName: pluginName,
			rule:       "federation_name",
			file:       "web/vite.config.ts",
			detail:     fmt.Sprintf("federation name is %q, expected %q", actualName, expectedName),
		}}
	}

	return nil
}