package format

import (
	"fmt"
	"regexp"
	"strconv"
)

// JobID bit layout constants — mirrors src/include/config.h.
//
//	|63     62|61        56|55       52|51         20|19      15|14          0|
//	|  TAG   | CLUSTER_ID | APISERVER_ID| TIMESTAMP  | SEQ_HIGH  | ARRAY_IDX  |
//	| 2 bits | 6 bits     | 4 bits      | 32 bits    | 5 bits    | 15 bits     |
const (
	nTagBits          = 2
	tagShift          = 62
	nClusterIDBits    = 6
	clusterIDShift    = 56
	nApiserverIDBits  = 4
	apiserverIDShift  = 52
	nTimestampBits    = 32
	timestampShift    = 20
	nArrayIdxBits     = 15
	sequenceHighShift = 15 // mirrors SEQUENCE_HIGH_SHIFT in config.h (== N_ARRAY_IDX_BITS)
	nSequenceBits     = 20 // N_JOBID_BITS(64) - N_CLUSTER_ID_BITS(6) - N_APISERVER_ID_BITS(4) - N_TIMESTAMP_BITS(32) - N_TAG_BITS(2) = 20
	tagJobArray       = 0x01
)

// extractBits extracts a bit field from id at the given shift position.
// Mirrors EXTRACT_BITS(id, shift, bits) in src/include/utils.h.
func extractBits(id uint64, shift, bits int) uint64 {
	mask := uint64((1 << bits) - 1)
	return (id >> shift) & mask
}

// FormatJobID decomposes a 64-bit packed job ID and formats it as a
// human-readable string matching the C fmt_jobid() format in src/lib/utils.c.
//   - Regular job:  "{cluster}-{apiserver}-{timestamp}-{sequence}"
//   - Array child:  "{cluster}-{apiserver}-{timestamp}-{base}[{idx}]"
func FormatJobID(uniqueJobID int64) string {
	id := uint64(uniqueJobID)
	clusterID := extractBits(id, clusterIDShift, nClusterIDBits)
	apiserverID := extractBits(id, apiserverIDShift, nApiserverIDBits)
	timestamp := extractBits(id, timestampShift, nTimestampBits)

	if (extractBits(id, tagShift, nTagBits) & tagJobArray) != 0 {
		// arrayBase mirrors EXTRACT_ARRAY_JOB: the seq_high bits shifted back to their
		// original position, matching C's fmt_jobid_ex output exactly.
		arrayBase := extractBits(id, sequenceHighShift, nSequenceBits-nArrayIdxBits) << uint(sequenceHighShift)
		arrayIdx := extractBits(id, 0, nArrayIdxBits)
		return fmt.Sprintf("%d-%d-%d-%d[%d]",
			clusterID, apiserverID, timestamp, arrayBase, arrayIdx)
	}
	sequence := extractBits(id, 0, nSequenceBits)
	return fmt.Sprintf("%d-%d-%d-%d",
		clusterID, apiserverID, timestamp, sequence)
}

// IsArrayJob returns true if the 64-bit packed job ID has the array job tag set.
func IsArrayJob(uniqueJobID int64) bool {
	return extractBits(uint64(uniqueJobID), tagShift, nTagBits)&tagJobArray != 0
}

// DecomposeJobID splits a 64-bit packed job ID into its component fields.
func DecomposeJobID(uniqueJobID int64) (clusterID, apiserverID, timestamp, sequence uint32, isArray bool, arrayIdx uint32) {
	id := uint64(uniqueJobID)
	clusterID = uint32(extractBits(id, clusterIDShift, nClusterIDBits))
	apiserverID = uint32(extractBits(id, apiserverIDShift, nApiserverIDBits))
	timestamp = uint32(extractBits(id, timestampShift, nTimestampBits))
	isArray = extractBits(id, tagShift, nTagBits)&tagJobArray != 0
	sequence = uint32(extractBits(id, 0, nSequenceBits))
	arrayIdx = uint32(extractBits(id, 0, nArrayIdxBits))
	return
}

// MakeJobID packs the components into a 64-bit job ID, mirroring MAKE_JOBID in src/include/utils.h.
func MakeJobID(clusterID, apiserverID, timestamp uint64, tag, sequence uint64) uint64 {
	return (clusterID << clusterIDShift) |
		(apiserverID << apiserverIDShift) |
		(timestamp << timestampShift) |
		(tag << tagShift) |
		sequence
}

var (
	// regexJobID matches "{int}-{int}-{int}-{int}" — mirrors REGEX_JOBID in config.h.
	regexJobID = regexp.MustCompile(`^\s*(\d+)-(\d+)-(\d+)-(\d+)\s*$`)
	// regexJobArrayID matches "{int}-{int}-{int}-{int}[{int}]" — mirrors REGEX_JOBARRAY_ID in config.h.
	regexJobArrayID = regexp.MustCompile(`^\s*(\d+)-(\d+)-(\d+)-(\d+)\[(\d+)\]\s*$`)
)

// ParseJobID parses a human-readable job ID string into a packed 64-bit job ID,
// mirroring parse_jobid() in src/lib/utils.c:482.
// Accepts: "0-0-12874529-0" (regular) or "0-0-12874529-0[5]" (array child).
func ParseJobID(s string) (uint64, error) {
	if m := regexJobArrayID.FindStringSubmatch(s); m != nil {
		clusterID, _ := strconv.ParseUint(m[1], 10, 64)
		apiserverID, _ := strconv.ParseUint(m[2], 10, 64)
		timestamp, _ := strconv.ParseUint(m[3], 10, 64)
		idJob, _ := strconv.ParseUint(m[4], 10, 64)
		idIdx, _ := strconv.ParseUint(m[5], 10, 64)
		return MakeJobID(clusterID, apiserverID, timestamp, tagJobArray, idJob+idIdx), nil
	}
	if m := regexJobID.FindStringSubmatch(s); m != nil {
		clusterID, _ := strconv.ParseUint(m[1], 10, 64)
		apiserverID, _ := strconv.ParseUint(m[2], 10, 64)
		timestamp, _ := strconv.ParseUint(m[3], 10, 64)
		idJob, _ := strconv.ParseUint(m[4], 10, 64)
		return MakeJobID(clusterID, apiserverID, timestamp, 0, idJob), nil
	}
	return 0, fmt.Errorf("invalid job ID format: %q", s)
}

// ExtractBaseJobID clears the tag and array_idx bits, returning the base job ID
// that the API server stores in the job_id column.
func ExtractBaseJobID(packed uint64) uint64 {
	id := packed &^ (uint64((1<<nTagBits)-1) << uint(tagShift)) // clear tag bits
	id = id &^ uint64((1<<nArrayIdxBits)-1)                     // clear array_idx bits
	return id
}

// FormatArrayChildID formats a job ID from a base job ID and array index.
// Used when only base+index are available (e.g. JobControlResponseItem).
func FormatArrayChildID(baseJobID int64, arrayIdx int) string {
	if arrayIdx == 0 {
		return FormatJobID(baseJobID)
	}
	uniqueID := uint64(baseJobID) | (uint64(tagJobArray) << uint(tagShift)) | uint64(arrayIdx)
	return FormatJobID(int64(uniqueID))
}

// ToAPIJobID converts a fmt_jobid-format string to the numeric form the API
// server expects ("{int}" or "{int}[{idx}]"). Plain integers pass through unchanged.
func ToAPIJobID(s string) (string, error) {
	if regexJobArrayID.MatchString(s) || regexJobID.MatchString(s) {
		packed, err := ParseJobID(s)
		if err != nil {
			return "", err
		}
		if IsArrayJob(int64(packed)) {
			baseID := ExtractBaseJobID(packed)
			arrayIdx := extractBits(packed, 0, nArrayIdxBits)
			return fmt.Sprintf("%d[%d]", baseID, arrayIdx), nil
		}
		return fmt.Sprintf("%d", packed), nil
	}
	return s, nil // already plain int or int[idx]
}