package backend

import (
	"apiserver/models"
	"encoding/json"
	"time"
	"fmt"
)

// 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 // mirrors TAG_JOB_ARRAY in config.h
)

// 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
}

// extractIDTag extracts the 2-bit tag field (bits 62-63).
// Mirrors EXTRACT_ID_TAG in src/include/utils.h.
func extractIDTag(id uint64) uint64 {
	return extractBits(id, tagShift, nTagBits)
}

// ExtractArrayBaseID extracts the base (family) job ID from a 64-bit encoded
// jobid. Mirrors C's array_jobid() in src/lib/utils.c and EXTRACT_ARRAY_BASEID
// in src/include/utils.h.
//   - For non-array jobs (tag=0x00): returns id unchanged.
//   - For array children (tag=0x01): returns the shared base ID (tag=0, idx=0).
func ExtractArrayBaseID(id uint64) uint64 {
	if extractIDTag(id) == 0x00 {
		return id
	}
	clusterID := extractBits(id, clusterIDShift, nClusterIDBits)
	apiserverID := extractBits(id, apiserverIDShift, nApiserverIDBits)
	timestamp := extractBits(id, timestampShift, nTimestampBits)
	// EXTRACT_ARRAY_JOB: high bits of sequence (mirrors config.h SEQUENCE_HIGH_SHIFT)
	arrayJob := extractBits(id, sequenceHighShift, nSequenceBits-nArrayIdxBits) << sequenceHighShift
	return (clusterID << clusterIDShift) |
		(apiserverID << apiserverIDShift) |
		(timestamp << timestampShift) |
		arrayJob // tag=0, idx=0
}

// ExtractArrayIdx extracts the array index from a 64-bit encoded jobid.
// Mirrors C's array_idx() in src/lib/utils.c and EXTRACT_ARRAY_IDX in
// src/include/utils.h.
// Returns 0 for non-array jobs (tag=0x00).
func ExtractArrayIdx(id uint64) int {
	if extractIDTag(id) == 0x00 {
		return 0
	}
	return int(extractBits(id, 0, nArrayIdxBits))
}

// IsArrayJob reports whether the 64-bit encoded jobid belongs to an array job
// (tag == TAG_JOB_ARRAY, 0x01). Returns false for non-array jobs (tag=0x00).
func IsArrayJob(id uint64) bool {
	return extractIDTag(id) == tagJobArray
}

// FormatJobID formats a packed 64-bit job ID as a human-readable string,
// matching the C fmt_jobid() output 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 extractIDTag(id) == tagJobArray {
		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)
}

// WorkerDefaultOutputPath returns the output file path the worker uses by default
// for the given job ID and task index, matching uv_proc.c make_job_output_path().
func WorkerDefaultOutputPath(uniqueJobID int64, taskIdx int) string {
	return fmt.Sprintf("/tmp/job_%s_task%d.out", FormatJobID(uniqueJobID), taskIdx)
}

// rawStartInfo mirrors the C job_startinfo_t fields used by the Go model.
type rawStartInfo struct {
	cmdline    string
	launchType string
	preExec    string
	postExec   string
	execHome   string
	execCWD    string
	execUser   string
}

// rawSubmitData mirrors the C job_submit_data_t fields used by the Go model.
type rawSubmitData struct {
	queue       string
	user        string
	jobName     string
	projectName string
	userGroup   string
	jobDesc     string
	resReq      string
	minTasks    int
	maxTasks    int
	startInfo   *rawStartInfo
}

// rawJobData mirrors the C xce_job_t fields used by the Go model.
type rawJobData struct {
	jobID      int64
	state      int
	runTime    int
	subTime    int64
	queueTime  int64
	startTime  int64
	finishTime int64
	submit     *rawSubmitData
	execHosts  []string
}

// rawWorkerData mirrors the C xce_worker_t fields used by the Go model.
type rawWorkerData struct {
	name      string
	status    int
	hasAttrs  bool
	hostType  string
	hostModel string
	cpuFactor float64
	maxCPUs   int
	maxMem    int
	maxSwap   int
	maxTmp    int
	nDisks    int
	resvals   []models.ResourceDistributionInfo
}

// rawQueueData mirrors the C xce_queue_t fields used by the Go model.
type rawQueueData struct {
	name     string
	status   int
	priority int
}

// rawResourceData mirrors the C xce_resource_t fields used by the Go model.
type rawResourceData struct {
	name     string
	desc     string
	valType  int
	ordType  int
	flags    int
	interval int
}

// rawJobToModel maps a rawJobData to a models.JobInfo.
// This pure-Go function contains the field-mapping logic and is tested without CGO.
func rawJobToModel(r rawJobData) *models.JobInfo {
	raw := uint64(r.jobID)
	info := &models.JobInfo{
		Unique_JobID: r.jobID,
		JobID:        int64(ExtractArrayBaseID(raw)),
		ArrayIdx:     ExtractArrayIdx(raw),
		JobStatus:    r.state,
		RunTime:      r.runTime,
	}
	if r.submit != nil {
		s := r.submit
		info.QueueName = s.queue
		info.SubmitUser = s.user
		info.JobName = s.jobName
		info.ProjectName = s.projectName
		info.UserGroup = s.userGroup
		info.JobDescription = s.jobDesc
		info.ResReq = s.resReq
		info.NumProcessors = s.minTasks
		info.MaxNumProcessors = s.maxTasks
		if s.startInfo != nil {
			si := s.startInfo
			info.Command = si.cmdline
			info.LaunchType = si.launchType
			info.PreExecCmd = si.preExec
			info.PostExecCmd = si.postExec
			info.ExecHome = si.execHome
			info.ExecCWD = si.execCWD
			info.ExecUser = si.execUser
		}
	}
	info.SubmitTime = r.subTime
	info.QueueTime = r.queueTime
	info.StartTime = r.startTime
	info.EndTime = r.finishTime
	if len(r.execHosts) > 0 {
		type hostSlot struct {
			HostName string `json:"host_name"`
			NumSlots int    `json:"num_slots"`
		}
		type execHostsJSON struct {
			HostSlots []hostSlot `json:"host_slots"`
			NumHosts  int        `json:"num_hosts"`
		}
		slots := make([]hostSlot, len(r.execHosts))
		for i, h := range r.execHosts {
			slots[i] = hostSlot{HostName: h, NumSlots: 1}
		}
		data, _ := json.Marshal(execHostsJSON{HostSlots: slots, NumHosts: len(slots)})
		info.ExecHosts = models.Jsonb{String: string(data)}
	}
	return info
}

// rawJobArrayToModels expands one compact (base jobid, array_size, one
// shared spec) array descriptor into N models.JobInfo entries locally, one
// per index in [0, array_size), using base_jobid + i arithmetic — the same
// arithmetic the controller's restore_job_array() (job.c) and the
// scheduler's sched_on_job_array() (handler.c) use to derive each
// element's identity (job-array-single-wal-record task 5.4, Req 6.2, 6.5).
// A freshly-received array element mirrors sched_on_job_array's
// make_array_element: JOB_STAT_PEND, receive-time sub_time — the compact
// wire descriptor carries no per-element timestamps to recover.
// Returns nil for a zero array_size or a nil submit (nothing to expand).
// Pure Go (no CGO) — cJobArrayToModels (convert.go) is the CGO adapter
// that decodes a *C.xce_job_submit_t into the rawSubmitData this consumes.
func rawJobArrayToModels(baseJobID uint64, arraySize uint64, submit *rawSubmitData) []*models.JobInfo {
	if arraySize == 0 || submit == nil {
		return nil
	}

	now := time.Now().Unix()
	out := make([]*models.JobInfo, 0, arraySize)
	for i := uint64(0); i < arraySize; i++ {
		r := rawJobData{
			jobID:   int64(baseJobID + i),
			state:   models.JOBSTAT["PEND"],
			subTime: now,
			submit:  submit,
		}
		out = append(out, rawJobToModel(r))
	}
	return out
}

// rawWorkerToModel maps a rawWorkerData to a models.HostInfo.
func rawWorkerToModel(r rawWorkerData) *models.HostInfo {
	info := &models.HostInfo{
		HostName:       r.name,
		HostStatus:     r.status,
		ResourceValues: r.resvals,
	}
	if r.hasAttrs {
		info.HostType = r.hostType
		info.HostModel = r.hostModel
		info.CPUFactor = r.cpuFactor
		info.NumCPUs = r.maxCPUs
		info.MaxMem = r.maxMem
		info.MaxSwap = r.maxSwap
		info.MaxTmp = r.maxTmp
		info.NumDisk = r.nDisks
	}
	return info
}

// rawQueueToModel maps a rawQueueData to a models.QueueInfo.
func rawQueueToModel(r rawQueueData) *models.QueueInfo {
	return &models.QueueInfo{
		QueueName:   r.name,
		QueueStatus: r.status,
		Priority:    r.priority,
	}
}

// rawResourceToModel maps a rawResourceData to a models.ResourceDefinitionInfo.
func rawResourceToModel(r rawResourceData) *models.ResourceDefinitionInfo {
	return &models.ResourceDefinitionInfo{
		ResourceName: r.name,
		Description:  r.desc,
		ValueType:    r.valType,
		OrderType:    r.ordType,
		Flag:         r.flags,
		Interval:     r.interval,
	}
}

// rawHostConfigData mirrors the C xce_hostconfig_t fields used by the Go model.
// Only fields that map to models.HostInfo are included:
//   - name → HostName, hostmodel → HostModel, hosttype → HostType, mxj → MaxSlot
//
// resources (xce_config_t**) and thresholds (xce_res_threshold_t**) have no HostInfo field and are excluded.
// dispatchwindow (xce_timewindow_config_t*) is deferred — DisptWindow is left as empty string.
type rawHostConfigData struct {
	name      string
	hostmodel string
	hosttype  string
	mxj       int
}

// rawHostConfigToModel maps a rawHostConfigData to a models.HostInfo.
// Config-sourced fields only; worker-sourced fields remain zero.
func rawHostConfigToModel(r rawHostConfigData) *models.HostInfo {
	return &models.HostInfo{
		HostName:  r.name,
		HostModel: r.hostmodel,
		HostType:  r.hosttype,
		MaxSlot:   r.mxj,
		// TODO(dispatchwindow): xce_hostconfig_t.dispatchwindow is xce_timewindow_config_t*
		// (nsegs int + segs[] with open/close time fields). Serializing it requires a Go
		// mirror struct and json.Marshal. Deferred: no API endpoint currently consumes
		// DisptWindow. Implement when /xce/v1/hosts returns dispatch window data.
	}
}

// rawResvalData mirrors the C xce_resval_t fields used by the Go model.
// IsDynamic is always true for push-sourced values (controller sends live measurements).
type rawResvalData struct {
	name     string
	host     string
	valWhich int // mirrors C xce_val_t.which (Value_u_* discriminant)
	i32      int32
	i64      int64
	u32      uint32
	u64      uint64
	fval     float64
	sval     string
	bval     bool
	valNil   bool // true when the C xce_val_t* was NULL
}

// rawResvalToDistribution maps a rawResvalData to a models.ResourceDistributionInfo.
// Returns nil when valNil is true (C val pointer was NULL) or when valWhich
// is an unknown discriminant — callers should skip nil results.
func rawResvalToDistribution(r rawResvalData) *models.ResourceDistributionInfo {
	rd := &models.ResourceDistributionInfo{
		ResourceName: r.name,
		Location:     r.host,
		IsDynamic:    true, // resource values pushed from workers are always dynamic
	}
	if r.valNil {
		return nil
	}
	switch r.valWhich {
	case 0: // Value_u_ivalue32
		rd.ValueType = int(models.NUMERIC)
		rd.NumericValue = float64(r.i32)
	case 2: // Value_u_ivalue64
		rd.ValueType = int(models.NUMERIC)
		rd.NumericValue = float64(r.i64)
	case 1: // Value_u_uvalue32
		rd.ValueType = int(models.NUMERIC)
		rd.NumericValue = float64(r.u32)
	case 3: // Value_u_uvalue64
		rd.ValueType = int(models.NUMERIC)
		rd.NumericValue = float64(r.u64)
	case 5: // Value_u_fvalue
		rd.ValueType = int(models.NUMERIC)
		rd.NumericValue = r.fval
	case 4: // Value_u_svalue
		rd.ValueType = int(models.STRING)
		rd.StringValue = r.sval
	case 6: // Value_u_bvalue
		rd.ValueType = int(models.BOOLEAN)
		rd.BooleanValue = r.bval
	default:
		return nil
	}
	return rd
}

// rawClusterData mirrors the C cluster_config_t fields used by the Go model.
// Only config-sourced fields are included (heartbeat_interval, vcpus, inactive_heartbeat_count).
// Built-in/sourced fields (Version, Status, ControllerName, etc.) come from LoadBuiltinData
// and are not part of the config push conversion.
type rawClusterData struct {
	name                   string
	heartbeatInterval      int
	vcpus                  int
	inactiveHeartbeatCount int
}

// rawClusterToModel maps a rawClusterData to a models.ClusterInfo.
// Config-sourced fields only; built-in fields remain zero.
func rawClusterToModel(r rawClusterData) *models.ClusterInfo {
	return &models.ClusterInfo{
		ClusterName:            r.name,
		HeartbeatInterval:      r.heartbeatInterval,
		Vcpus:                  r.vcpus,
		InactiveHeartbeatCount: r.inactiveHeartbeatCount,
	}
}