package lint

import (
	"sort"

	"git.warky.dev/wdevs/pgtidy/pkg/diagnostics"
)

// ApplyFixes applies all autofixes from diags to src and returns the result.
// Fixes are applied in reverse-offset order so earlier edits do not shift the
// byte positions of later ones. Overlapping fixes are skipped.
func ApplyFixes(src string, diags []diagnostics.Diagnostic) string {
	type fix struct {
		offset, end int
		new         string
	}
	var fixes []fix
	for _, d := range diags {
		if d.Fix != nil {
			fixes = append(fixes, fix{d.Fix.Offset, d.Fix.End, d.Fix.New})
		}
	}
	if len(fixes) == 0 {
		return src
	}
	sort.Slice(fixes, func(i, j int) bool {
		return fixes[i].offset > fixes[j].offset
	})
	b := []byte(src)
	last := len(b) + 1 // sentinel: no fix applied yet
	for _, f := range fixes {
		if f.end > last {
			continue // overlaps a previously applied fix; skip
		}
		last = f.offset
		b = append(b[:f.offset], append([]byte(f.new), b[f.end:]...)...)
	}
	return string(b)
}