package semver

import (
	"fmt"
	"strings"

	goSemver "github.com/Masterminds/semver/v3"

	"github.com/thokra/stamp/internal/changeset"
)

// Bump computes the next version given the current version string and a bump type.
// preID is the pre-release identifier (e.g. "alpha", "beta", "rc") used for pre-* bumps.
func Bump(current string, bump changeset.BumpType, preID string) (string, error) {
	v, err := goSemver.NewVersion(current)
	if err != nil {
		return "", fmt.Errorf("invalid version %q: %w", current, err)
	}

	if preID == "" {
		preID = "0"
	}

	switch bump {
	case changeset.BumpMajor:
		next := v.IncMajor()
		return next.Original(), nil

	case changeset.BumpMinor:
		next := v.IncMinor()
		return next.Original(), nil

	case changeset.BumpPatch:
		next := v.IncPatch()
		return next.Original(), nil

	case changeset.BumpPreMajor:
		next := v.IncMajor()
		pre, err := goSemver.NewVersion(fmt.Sprintf("%d.%d.%d-%s.0", next.Major(), next.Minor(), next.Patch(), preID))
		if err != nil {
			return "", err
		}
		return pre.Original(), nil

	case changeset.BumpPreMinor:
		next := v.IncMinor()
		pre, err := goSemver.NewVersion(fmt.Sprintf("%d.%d.%d-%s.0", next.Major(), next.Minor(), next.Patch(), preID))
		if err != nil {
			return "", err
		}
		return pre.Original(), nil

	case changeset.BumpPrePatch:
		next := v.IncPatch()
		pre, err := goSemver.NewVersion(fmt.Sprintf("%d.%d.%d-%s.0", next.Major(), next.Minor(), next.Patch(), preID))
		if err != nil {
			return "", err
		}
		return pre.Original(), nil

	case changeset.BumpPreRelease:
		// If already a pre-release with matching identifier, increment the pre-release number.
		// Otherwise start a fresh pre-release on current patch.
		preStr := v.Prerelease()
		if preStr != "" && strings.HasPrefix(preStr, preID+".") {
			parts := strings.SplitN(preStr, ".", 2)
			var num int
			fmt.Sscanf(parts[1], "%d", &num)
			next, err := goSemver.NewVersion(fmt.Sprintf("%d.%d.%d-%s.%d",
				v.Major(), v.Minor(), v.Patch(), preID, num+1))
			if err != nil {
				return "", err
			}
			return next.Original(), nil
		}
		// Start a new pre-release on next patch.
		patch := v.IncPatch()
		next, err := goSemver.NewVersion(fmt.Sprintf("%d.%d.%d-%s.0",
			patch.Major(), patch.Minor(), patch.Patch(), preID))
		if err != nil {
			return "", err
		}
		return next.Original(), nil

	default:
		return "", fmt.Errorf("unknown bump type %q", bump)
	}
}

// HighestBump returns the highest-priority bump type from a set of bumps.
// Priority: major > minor > patch > premajor > preminor > prepatch > prerelease.
func HighestBump(bumps []changeset.BumpType) changeset.BumpType {
	priority := map[changeset.BumpType]int{
		changeset.BumpMajor:      6,
		changeset.BumpMinor:      5,
		changeset.BumpPatch:      4,
		changeset.BumpPreMajor:   3,
		changeset.BumpPreMinor:   2,
		changeset.BumpPrePatch:   1,
		changeset.BumpPreRelease: 0,
	}

	best := changeset.BumpPreRelease
	bestP := -1
	for _, b := range bumps {
		if p, ok := priority[b]; ok && p > bestP {
			best = b
			bestP = p
		}
	}
	return best
}

// ProjectBumps aggregates bump types per project from a list of changesets.
func ProjectBumps(changesets []*changeset.Changeset) map[string][]changeset.BumpType {
	result := map[string][]changeset.BumpType{}
	for _, cs := range changesets {
		for project, bump := range cs.Bumps {
			result[project] = append(result[project], bump)
		}
	}
	return result
}