package gitea

import (
	"strconv"
	"strings"
)

// DiffLineRanges maps filenames to the set of new-file line numbers present in the diff.
type DiffLineRanges struct {
	files map[string]map[int]bool
}

// Contains reports whether the given file+line is within the diff hunks.
func (d *DiffLineRanges) Contains(file string, line int) bool {
	if d == nil || d.files == nil {
		return false
	}
	lines, ok := d.files[file]
	if !ok {
		return false
	}
	return lines[line]
}

// ParseDiffNewLines parses a unified diff and extracts the new-file line numbers
// that appear in each hunk (both added and context lines).
func ParseDiffNewLines(diff string) *DiffLineRanges {
	result := &DiffLineRanges{files: make(map[string]map[int]bool)}

	var currentFile string
	var newLine int

	for _, line := range strings.Split(diff, "\n") {
		// Track current file from +++ header
		if strings.HasPrefix(line, "+++ b/") {
			currentFile = strings.TrimPrefix(line, "+++ b/")
			if result.files[currentFile] == nil {
				result.files[currentFile] = make(map[int]bool)
			}
			continue
		}
		if strings.HasPrefix(line, "+++ /dev/null") {
			currentFile = ""
			continue
		}

		// Parse hunk header: @@ -old,count +new,count @@ or @@ -old +new @@
		if strings.HasPrefix(line, "@@") && currentFile != "" {
			// Extract the +N part — handle both "+10,8" and "+1" forms
			parts := strings.Split(line, "+")
			if len(parts) >= 2 {
				// Take everything before comma or space
				numStr := parts[1]
				if idx := strings.IndexAny(numStr, ", "); idx != -1 {
					numStr = numStr[:idx]
				}
				n, err := strconv.Atoi(numStr)
				if err == nil {
					newLine = n
				}
			}
			continue
		}

		if currentFile == "" {
			continue
		}

		// Skip diff metadata lines
		if strings.HasPrefix(line, "\\") {
			continue
		}

		// Count lines in hunk
		if strings.HasPrefix(line, "+") || strings.HasPrefix(line, " ") {
			result.files[currentFile][newLine] = true
			newLine++
		} else if strings.HasPrefix(line, "-") {
			// Removed lines don't advance new line counter
			continue
		}
	}

	return result
}