package git

import (
    "fmt"
    "strings"
)

// Cf. https://git.kernel.org/pub/scm/git/git.git/tree/Documentation/gitformat-pack.txt?id=bcb6cae2966cc407ca1afc77413b3ef11103c175#n72
type ObjectType int
const (
    // OBJ_BAD represents an invalid object type
    OBJ_BAD = ObjectType(iota)

    // OBJ_COMMIT, OBJ_TREE, OBJ_BLOB, OBJ_TAG are 
    // Cf. https://git.kernel.org/pub/scm/git/git.git/tree/Documentation/gitformat-pack.txt?id=bcb6cae2966cc407ca1afc77413b3ef11103c175#n97 [accessed 2023-09-30]
    OBJ_COMMIT
    OBJ_TREE
    OBJ_BLOB
    OBJ_TAG

    // object type 5 is unused
    _

    // OBJ_OFS_DELTA, OBJ_REF_DELTA are [TODO:write]
    OBJ_OFS_DELTA
    OBJ_REF_DELTA
)

func (objtyp ObjectType) String() string {
    switch objtyp {
    default:
        // TODO consider
        //panic("unreachable")
        return fmt.Sprintf("OBJ_BAD(%d)", int(objtyp))
    case OBJ_COMMIT:
        return "OBJ_COMMIT"
    case OBJ_TREE:
        return "OBJ_TREE"
    case OBJ_BLOB:
        return "OBJ_BLOB"
    case OBJ_TAG:
        return "OBJ_TAG"
    case OBJ_OFS_DELTA:
        return "OBJ_OFS_DELTA"
    case OBJ_REF_DELTA:
        return "OBJ_REF_DELTA"
    }
}

// Deprecated: TODO ugly name
func (objtyp ObjectType) LowercaseName(padded bool) string {
    p := func(n int) string {
        if !padded {
            n = 0
        }
        return strings.Repeat(" ", n)
    }
    switch objtyp {
    case OBJ_COMMIT:
        return "commit"
    case OBJ_TREE:
        return "tree" + p(2)
    case OBJ_BLOB:
        return "blob" + p(2)
    default:
        panic(fmt.Sprintf("%s.LowercaseName", objtyp))
    }
}

func ObjectID(alg ChecksumAlgorithm, objtyp ObjectType, data []byte) Checksum {
    switch objtyp {
    case OBJ_COMMIT, OBJ_TREE, OBJ_BLOB:
        return alg.Slurp([]byte(fmt.Sprintf("%s %d\x00", objtyp.LowercaseName(false), len(data))), data)
    default:
        panic(fmt.Errorf("ObjectID: unexpected objtyp=%s", objtyp))
    }
}