package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"

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

type presetViolation struct {
	file    string
	message string
}

type presetJSON struct {
	ID          string      `json:"id"`
	Name        string      `json:"name"`
	Description string      `json:"description"`
	Theme       theme.Theme `json:"theme"`
}

func checkPresets(root string) []presetViolation {
	var violations []presetViolation

	presetsFiles := findPresetsFiles(root)
	for _, path := range presetsFiles {
		relPath, _ := filepath.Rel(root, path)
		if relPath == "" {
			relPath = path
		}

		data, err := os.ReadFile(path)
		if err != nil {
			violations = append(violations, presetViolation{
				file:    relPath,
				message: fmt.Sprintf("cannot read file: %v", err),
			})
			continue
		}

		// Strict unmarshal: catches type mismatches (e.g., int where string expected)
		var presets []presetJSON
		decoder := json.NewDecoder(bytes.NewReader(data))
		decoder.DisallowUnknownFields()
		if err := decoder.Decode(&presets); err != nil {
			// Distinguish between unknown fields (warning-worthy) and hard parse errors
			if isUnknownFieldError(err) {
				// Re-try without strict mode to get the actual parse result
				var lenient []presetJSON
				if lenientErr := json.Unmarshal(data, &lenient); lenientErr != nil {
					violations = append(violations, presetViolation{
						file:    relPath,
						message: fmt.Sprintf("invalid JSON: %v", lenientErr),
					})
				} else {
					violations = append(violations, presetViolation{
						file:    relPath,
						message: fmt.Sprintf("unknown fields (stale preset data): %v", err),
					})
				}
			} else {
				violations = append(violations, presetViolation{
					file:    relPath,
					message: fmt.Sprintf("invalid JSON: %v", err),
				})
			}
			continue
		}

		for i, p := range presets {
			if p.ID == "" {
				violations = append(violations, presetViolation{
					file:    relPath,
					message: fmt.Sprintf("preset[%d]: missing \"id\" field", i),
				})
			}
			if p.Name == "" {
				violations = append(violations, presetViolation{
					file:    relPath,
					message: fmt.Sprintf("preset[%d]: missing \"name\" field", i),
				})
			}
		}
	}

	return violations
}

func findPresetsFiles(root string) []string {
	var files []string
	_ = filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() {
			if info != nil && info.IsDir() {
				switch info.Name() {
				case ".git", ".worktrees", "vendor", "node_modules", "web", "dist":
					return filepath.SkipDir
				}
			}
			return nil
		}
		if info.Name() == "presets.json" {
			files = append(files, path)
		}
		return nil
	})
	return files
}

func isUnknownFieldError(err error) bool {
	return strings.Contains(err.Error(), "unknown field")
}