package main

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

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

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

var (
	// PostCSS config: bare tailwindcss plugin (v3 syntax)
	rePostCSSBarePlugin = regexp.MustCompile(`(?:['"]?tailwindcss['"]?\s*:|['"]tailwindcss['"])`)

	// PostCSS config: correct v4 plugin
	rePostCSSV4Plugin = regexp.MustCompile(`@tailwindcss/postcss`)

	// CSS: old @tailwind directives (v3)
	reTailwindDirective = regexp.MustCompile(`^\s*@tailwind\s+(base|components|utilities)`)

	// CSS: v4 import
	reTailwindV4Import = regexp.MustCompile(`@import\s+["']tailwindcss["']`)

	// CSS: @config directive
	reCSSConfigDirective = regexp.MustCompile(`^\s*@config\s+`)

	// CSS: old autoprefixer in postcss config (unnecessary with v4)
	rePostCSSAutoprefixer = regexp.MustCompile(`(?:['"]?autoprefixer['"]?\s*:|['"]autoprefixer['"])`)
)

func checkTailwindV4(frontendDir string) []tailwindViolation {
	var violations []tailwindViolation

	projectDir := filepath.Dir(frontendDir)

	for _, v := range checkPostCSSConfig(projectDir) {
		v.file = filepath.Clean(filepath.Join("..", v.file))
		violations = append(violations, v)
	}
	violations = append(violations, checkCSSDirectives(frontendDir, projectDir)...)

	return violations
}

func checkPostCSSConfig(projectDir string) []tailwindViolation {
	var violations []tailwindViolation

	configNames := []string{"postcss.config.js", "postcss.config.mjs", "postcss.config.cjs", "postcss.config.ts", ".postcssrc", ".postcssrc.js", ".postcssrc.json"}

	for _, name := range configNames {
		configPath := filepath.Join(projectDir, name)
		if !fileExists(configPath) {
			continue
		}

		violations = append(violations, scanPostCSSFile(configPath, name)...)
	}

	return violations
}

func scanPostCSSFile(configPath, name string) []tailwindViolation {
	var violations []tailwindViolation

	f, err := os.Open(configPath)
	if err != nil {
		return nil
	}
	defer helpers.LogDeferredError(nil, "close postcss config file", f.Close, "path", configPath)

	scanner := bufio.NewScanner(f)
	lineNum := 0
	hasV4Plugin := false
	for scanner.Scan() {
		lineNum++
		line := scanner.Text()

		if rePostCSSV4Plugin.MatchString(line) {
			hasV4Plugin = true
		}

		if rePostCSSBarePlugin.MatchString(line) && !rePostCSSV4Plugin.MatchString(line) {
			violations = append(violations, tailwindViolation{
				file:    name,
				line:    lineNum,
				rule:    "postcss-v4-plugin",
				snippet: strings.TrimSpace(line),
			})
		}

		if hasV4Plugin && rePostCSSAutoprefixer.MatchString(line) {
			violations = append(violations, tailwindViolation{
				file:    name,
				line:    lineNum,
				rule:    "postcss-no-autoprefixer",
				snippet: strings.TrimSpace(line),
			})
		}
	}

	return violations
}

func checkCSSDirectives(frontendDir, projectDir string) []tailwindViolation {
	var violations []tailwindViolation

	hasTailwindConfig := fileExists(filepath.Join(projectDir, "tailwind.config.ts")) ||
		fileExists(filepath.Join(projectDir, "tailwind.config.js"))

	if err := filepath.Walk(frontendDir, func(path string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() {
			return nil
		}
		if !strings.HasSuffix(path, ".css") {
			return nil
		}
		if strings.Contains(path, "node_modules") || strings.Contains(path, "/dist/") {
			return nil
		}

		relPath, _ := filepath.Rel(frontendDir, path)
		if relPath == "" {
			relPath = path
		}

		f, openErr := os.Open(path)
		if openErr != nil {
			return nil
		}
		defer helpers.LogDeferredError(nil, "close CSS file for tailwind scan", f.Close, "path", path)

		scanner := bufio.NewScanner(f)
		lineNum := 0
		hasTailwindImport := false
		hasConfigDirective := false

		for scanner.Scan() {
			lineNum++
			line := scanner.Text()

			if reTailwindV4Import.MatchString(line) {
				hasTailwindImport = true
			}
			if reCSSConfigDirective.MatchString(line) {
				hasConfigDirective = true
			}

			if reTailwindDirective.MatchString(line) {
				violations = append(violations, tailwindViolation{
					file:    relPath,
					line:    lineNum,
					rule:    "css-v4-import",
					snippet: strings.TrimSpace(line),
				})
			}
		}

		if hasTailwindImport && hasTailwindConfig && !hasConfigDirective {
			violations = append(violations, tailwindViolation{
				file:    relPath,
				line:    0,
				rule:    "css-missing-config",
				snippet: "uses @import \"tailwindcss\" but missing @config directive (tailwind.config.* exists)",
			})
		}

		return nil
	}); err != nil {
		violations = append(violations, tailwindViolation{
			file:    frontendDir,
			line:    0,
			rule:    "walk-error",
			snippet: err.Error(),
		})
	}

	return violations
}