package gitcmd

import (
	"strconv"
	"strings"
)

type CompareResult struct {
	Base    string      `json:"base"`
	Head    string      `json:"head"`
	Ahead   int         `json:"ahead"`
	Behind  int         `json:"behind"`
	Commits []Commit    `json:"commits"`
	Diff    DiffResult  `json:"diff"`
}

func (r *Repository) Compare(base, head string) (*CompareResult, error) {
	if base == "" {
		base = "HEAD"
	}
	if head == "" {
		head = "HEAD"
	}

	ahead, behind, err := r.countAheadBehind(base, head)
	if err != nil {
		return nil, err
	}

	commits, err := r.ListCommits(base+".."+head, 0)
	if err != nil {
		return nil, err
	}

	diff, err := r.Diff(base, head, nil)
	if err != nil {
		return nil, err
	}

	return &CompareResult{
		Base:    base,
		Head:    head,
		Ahead:   ahead,
		Behind:  behind,
		Commits: commits,
		Diff:    *diff,
	}, nil
}

func (r *Repository) countAheadBehind(base, head string) (ahead, behind int, err error) {
	out, _, err := NewCommand("rev-list", "--left-right", "--count").
		AddDynamicArguments(base + "..." + head).
		WithDir(r.Path).
		RunStdString(r.ctx)
	if err != nil {
		return 0, 0, err
	}
	parts := strings.Fields(strings.TrimSpace(out))
	if len(parts) >= 2 {
		behind, _ = strconv.Atoi(parts[0])
		ahead, _ = strconv.Atoi(parts[1])
	}
	return ahead, behind, nil
}