package main

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

	"git.dev.alexdunmow.com/block/check-safety/internal/helpers"
)

type htmlSanitizeViolation struct {
	file    string
	line    int
	rule    string
	snippet string
}

var htmlSanitizePatterns = []struct {
	pattern *regexp.Regexp
	rule    string
}{
	{
		pattern: regexp.MustCompile(`regexp\.\s*(?:MustCompile|Compile)\s*\(.+<(?:script|style)\b`),
		rule:    "regex-html-strip",
	},
	{
		pattern: regexp.MustCompile(`regexp\.\s*(?:MustCompile|Compile)\s*\(.+<\[\^`),
		rule:    "regex-html-strip",
	},
	{
		pattern: regexp.MustCompile(`(?:func\s+(?:strip|Strip)HTML|func\s+stripHTMLTags|func\s+sanitizeHTML|func\s+cleanHTML)\s*\(`),
		rule:    "hand-rolled-strip-func",
	},
	{
		pattern: regexp.MustCompile(`if\s+r\s*==\s*'<'\s*\{`),
		rule:    "char-by-char-tag-strip",
	},
	{
		pattern: regexp.MustCompile(`strings\.NewReplacer\(.*"<[^"]*>".*\)`),
		rule:    "replacer-html-strip",
	},
}

var htmlSanitizeAllowedFiles = map[string]bool{
	"cmd/check-safety/htmlsanitize.go":      true,
	"cmd/check-safety/check_htmlsanitize.go": true, // holds the fix-instruction table (example patterns)
	"cmd/check-safety/main.go":              true,
	"internal/helpers/slug.go":              true,
}

func isHTMLSanitizeAllowed(relPath string) bool {
	if strings.HasSuffix(relPath, "_test.go") {
		return true
	}
	for allowed := range htmlSanitizeAllowedFiles {
		if strings.HasSuffix(relPath, allowed) {
			return true
		}
	}
	return false
}

func checkHTMLSanitize(root string) []htmlSanitizeViolation {
	var violations []htmlSanitizeViolation

	_ = filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() || !strings.HasSuffix(path, ".go") {
			return nil
		}
		if strings.Contains(path, "/vendor/") {
			return nil
		}

		relPath, _ := filepath.Rel(root, path)
		if isHTMLSanitizeAllowed(relPath) {
			return nil
		}

		f, ferr := os.Open(path)
		if ferr != nil {
			return nil
		}
		defer helpers.LogDeferredError(nil, "close html-sanitize scan file", f.Close, "path", path)

		scanner := bufio.NewScanner(f)
		lineNum := 0
		for scanner.Scan() {
			lineNum++
			line := scanner.Text()
			trimmed := strings.TrimSpace(line)

			if strings.HasPrefix(trimmed, "//") {
				continue
			}

			for _, check := range htmlSanitizePatterns {
				if check.pattern.MatchString(line) {
					violations = append(violations, htmlSanitizeViolation{
						file:    relPath,
						line:    lineNum,
						rule:    check.rule,
						snippet: strings.TrimSpace(line),
					})
				}
			}
		}
		return nil
	})

	return violations
}