package redaction

import (
	"fmt"
	"strings"
	"unicode/utf8"
)

type RedactionResult struct {
	Text     string
	Applied  bool
	Findings []Finding
}

type Finding struct {
	Type  string
	Count int
}

type Redactor interface {
	RedactText(input string) RedactionResult
	RedactJSON(input map[string]any) map[string]any
	RedactBytesForLog(input []byte) string
}

type DefaultRedactor struct{}

func New() DefaultRedactor { return DefaultRedactor{} }

func (DefaultRedactor) RedactText(input string) RedactionResult {
	out := input
	counts := map[string]int{}
	apply := func(kind string, fn func(string) string) {
		before := out
		out = fn(out)
		if out != before {
			counts[kind]++
		}
	}
	apply("database_url", func(s string) string { return databaseURLPattern.ReplaceAllString(s, `${1}:***MASKED***@`) })
	apply("api_key", func(s string) string { return openAIKeyPattern.ReplaceAllString(s, `sk-***MASKED***`) })
	apply("bearer", func(s string) string { return bearerPattern.ReplaceAllString(s, `Bearer ***MASKED***`) })
	apply("secret", func(s string) string { return secretKVPattern.ReplaceAllString(s, `${1}=***MASKED***`) })
	apply("email", func(s string) string { return emailPattern.ReplaceAllString(s, `${1}***${3}`) })
	apply("otp", func(s string) string {
		return otpPattern.ReplaceAllStringFunc(s, func(m string) string {
			if strings.Contains(strings.ToLower(m), "услуг") {
				return m
			}
			parts := otpPattern.FindStringSubmatch(m)
			if len(parts) != 3 {
				return m
			}
			return parts[1] + "CODE"
		})
	})
	apply("account", func(s string) string {
		return accountPattern.ReplaceAllStringFunc(s, func(m string) string {
			parts := accountPattern.FindStringSubmatch(m)
			if len(parts) != 3 {
				return m
			}
			return parts[1] + maskMiddle(parts[2], 0, 4, "****")
		})
	})
	apply("phone", func(s string) string {
		return phonePattern.ReplaceAllStringFunc(s, func(m string) string { return maskMiddle(m, 4, 4, "***") })
	})
	apply("iin", func(s string) string {
		return digits12Pattern.ReplaceAllStringFunc(s, func(m string) string { return maskMiddle(m, 4, 4, "****") })
	})
	apply("card", func(s string) string {
		return digits16Pattern.ReplaceAllStringFunc(s, func(m string) string { return maskMiddle(m, 4, 4, "********") })
	})
	findings := make([]Finding, 0, len(counts))
	for k, v := range counts {
		findings = append(findings, Finding{Type: k, Count: v})
	}
	return RedactionResult{Text: out, Applied: out != input, Findings: findings}
}

func (r DefaultRedactor) RedactJSON(input map[string]any) map[string]any {
	return redactMap(r, input)
}

func (DefaultRedactor) RedactBytesForLog(input []byte) string {
	return fmt.Sprintf("[bytes:%d redacted]", len(input))
}

func redactMap(r DefaultRedactor, input map[string]any) map[string]any {
	out := map[string]any{}
	for k, v := range input {
		out[k] = redactValue(r, v)
	}
	return out
}

func redactValue(r DefaultRedactor, v any) any {
	switch x := v.(type) {
	case string:
		return r.RedactText(x).Text
	case map[string]any:
		return redactMap(r, x)
	case []any:
		out := make([]any, len(x))
		for i := range x {
			out[i] = redactValue(r, x[i])
		}
		return out
	case []string:
		out := make([]string, len(x))
		for i := range x {
			out[i] = r.RedactText(x[i]).Text
		}
		return out
	default:
		return v
	}
}

func maskMiddle(value string, keepStart, keepEnd int, mask string) string {
	if !utf8.ValidString(value) {
		return "***MASKED***"
	}
	r := []rune(value)
	if keepStart == 0 && keepEnd > 0 {
		if len(r) <= keepEnd {
			return mask
		}
		return mask + string(r[len(r)-keepEnd:])
	}
	if len(r) <= keepStart+keepEnd {
		return strings.Repeat("*", len(r))
	}
	return string(r[:keepStart]) + mask + string(r[len(r)-keepEnd:])
}