package main

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

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

var (
	// Matches: const { ... } = useQuery — destructuring pattern
	reQueryDestructure = regexp.MustCompile(`(?:const|let|var)\s+\{([^}]+)\}\s*=\s*useQuery`)

	// Matches: useMutation( — start of a mutation hook call
	reUseMutation = regexp.MustCompile(`\buseMutation\s*\(`)

	// Matches: onError in options
	reOnError = regexp.MustCompile(`onError\s*:`)

	// Matches: catch or .catch(
	reCatch = regexp.MustCompile(`\bcatch\b`)

	// Matches: toast.error
	reToastError = regexp.MustCompile(`toast\.error\s*\(`)
)

// checkRPCErrors detects missing error handling for RPC queries and mutations.
func checkRPCErrors(webSrcDir string) (violations []rpcErrorViolation, warnings []rpcErrorViolation) {
	globalMutationHandler := hasGlobalMutationErrorHandler(webSrcDir)

	if err := filepath.Walk(webSrcDir, func(path string, info os.FileInfo, err error) error {
		if err != nil || info.IsDir() {
			return nil
		}
		ext := filepath.Ext(path)
		if ext != ".tsx" && ext != ".ts" {
			return nil
		}
		if strings.Contains(path, "node_modules") || strings.Contains(path, "/dist/") {
			return nil
		}

		relPath, _ := filepath.Rel(webSrcDir, path)

		// Only check components/ and routes/
		if !strings.HasPrefix(relPath, "components/") && !strings.HasPrefix(relPath, "routes/") {
			return nil
		}

		data, err := os.ReadFile(path)
		if err != nil {
			return nil
		}
		lines := strings.Split(string(data), "\n")
		fullContent := string(data)

		for i, line := range lines {
			lineNum := i + 1
			trimmed := strings.TrimSpace(line)

			// Skip comments
			if strings.HasPrefix(trimmed, "//") || strings.HasPrefix(trimmed, "*") || strings.HasPrefix(trimmed, "{/*") {
				continue
			}

			// Check useQuery destructuring for missing error
			if reQueryDestructure.MatchString(line) {
				matches := reQueryDestructure.FindStringSubmatch(line)
				if len(matches) > 1 {
					destructured := matches[1]
					if !strings.Contains(destructured, "error") {
						warnings = append(warnings, rpcErrorViolation{
							file:    relPath,
							line:    lineNum,
							rule:    "query-no-error",
							snippet: strings.TrimSpace(line),
						})
					}
				}
			}

			// Check useMutation — find mutations with no error handling anywhere in file
			if reUseMutation.MatchString(line) && !strings.HasPrefix(trimmed, "//") {
				// Check if this mutation's options or its call sites have error handling
				// Look in the surrounding context (next 20 lines) for onError
				hasErrorHandling := false

				// Check the mutation definition options (same line or next few lines)
				for j := i; j < len(lines) && j <= i+15; j++ {
					if reOnError.MatchString(lines[j]) {
						hasErrorHandling = true
						break
					}
					// Stop at next statement
					if j > i && (strings.Contains(lines[j], "const ") || strings.Contains(lines[j], "return ")) {
						break
					}
				}

				// Check if the file has ANY try/catch or toast.error (broad heuristic)
				if !hasErrorHandling {
					if reCatch.MatchString(fullContent) || reToastError.MatchString(fullContent) {
						// File has some error handling — mutation call sites likely handle it
						hasErrorHandling = true
					}
				}

				if !hasErrorHandling && !globalMutationHandler {
					violations = append(violations, rpcErrorViolation{
						file:    relPath,
						line:    lineNum,
						rule:    "mutation-no-error-handler",
						snippet: strings.TrimSpace(line),
					})
				}
			}
		}

		return nil
	}); err != nil {
		_ = err // Walk errors are non-fatal for safety checks
	}

	return violations, warnings
}

func hasGlobalMutationErrorHandler(webSrcDir string) bool {
	queryClientPath := filepath.Join(webSrcDir, "lib", "query-client.ts")
	data, err := os.ReadFile(queryClientPath)
	if err != nil {
		return false
	}

	content := string(data)
	return strings.Contains(content, "MutationCache") && strings.Contains(content, "onError")
}