package blockstm

import (
	"fmt"

	"github.com/ethereum/go-ethereum/log"
)

type ExecResult struct {
	err      error
	ver      Version
	txIn     TxnInput
	txOut    TxnOutput
	txAllOut TxnOutput
}

type ExecTask interface {
	Execute(mvh *MVHashMap, incarnation int) error
	MVReadList() []ReadDescriptor
	MVWriteList() []WriteDescriptor
	MVFullWriteList() []WriteDescriptor
}

type ExecVersionView struct {
	ver Version
	et  ExecTask
	mvh *MVHashMap
}

func (ev *ExecVersionView) Execute() (er ExecResult) {
	er.ver = ev.ver
	if er.err = ev.et.Execute(ev.mvh, ev.ver.Incarnation); er.err != nil {
		log.Debug("blockstm executed task failed", "Tx index", ev.ver.TxnIndex, "incarnation", ev.ver.Incarnation, "err", er.err)
		return
	}

	er.txIn = ev.et.MVReadList()
	er.txOut = ev.et.MVWriteList()
	er.txAllOut = ev.et.MVFullWriteList()
	log.Debug("blockstm executed task", "Tx index", ev.ver.TxnIndex, "incarnation", ev.ver.Incarnation, "err", er.err)

	return
}

var ErrExecAbort = fmt.Errorf("execution aborted with dependency")

const numGoProcs = 4

// nolint: gocognit
func ExecuteParallel(tasks []ExecTask) (lastTxIO *TxnInputOutput, err error) {
	if len(tasks) == 0 {
		return MakeTxnInputOutput(len(tasks)), nil
	}

	chTasks := make(chan ExecVersionView, len(tasks))
	chResults := make(chan ExecResult, len(tasks))
	chDone := make(chan bool)

	var cntExec, cntSuccess, cntAbort, cntTotalValidations, cntValidationFail int

	for i := 0; i < numGoProcs; i++ {
		go func(procNum int, t chan ExecVersionView) {
		Loop:
			for {
				select {
				case task := <-t:
					{
						res := task.Execute()
						chResults <- res
					}
				case <-chDone:
					break Loop
				}
			}
			log.Debug("blockstm", "proc done", procNum) // TODO: logging ...
		}(i, chTasks)
	}

	mvh := MakeMVHashMap()

	execTasks := makeStatusManager(len(tasks))
	validateTasks := makeStatusManager(0)

	// bootstrap execution
	for x := 0; x < numGoProcs; x++ {
		tx := execTasks.takeNextPending()
		if tx != -1 {
			cntExec++

			log.Debug("blockstm", "bootstrap: proc", x, "executing task", tx)
			chTasks <- ExecVersionView{ver: Version{tx, 0}, et: tasks[tx], mvh: mvh}
		}
	}

	lastTxIO = MakeTxnInputOutput(len(tasks))
	txIncarnations := make([]int, len(tasks))

	diagExecSuccess := make([]int, len(tasks))
	diagExecAbort := make([]int, len(tasks))

	for {
		res := <-chResults
		switch res.err {
		case nil:
			{
				mvh.FlushMVWriteSet(res.txAllOut)
				lastTxIO.recordRead(res.ver.TxnIndex, res.txIn)
				if res.ver.Incarnation == 0 {
					lastTxIO.recordWrite(res.ver.TxnIndex, res.txOut)
					lastTxIO.recordAllWrite(res.ver.TxnIndex, res.txAllOut)
				} else {
					if res.txAllOut.hasNewWrite(lastTxIO.AllWriteSet(res.ver.TxnIndex)) {
						log.Debug("blockstm", "Revalidate completed txs greater than current tx: ", res.ver.TxnIndex)
						validateTasks.pushPendingSet(execTasks.getRevalidationRange(res.ver.TxnIndex))
					}

					prevWrite := lastTxIO.AllWriteSet(res.ver.TxnIndex)

					// Remove entries that were previously written but are no longer written

					cmpMap := make(map[string]bool)

					for _, w := range res.txAllOut {
						cmpMap[string(w.Path)] = true
					}

					for _, v := range prevWrite {
						if _, ok := cmpMap[string(v.Path)]; !ok {
							mvh.Delete(v.Path, res.ver.TxnIndex)
						}
					}

					lastTxIO.recordWrite(res.ver.TxnIndex, res.txOut)
					lastTxIO.recordAllWrite(res.ver.TxnIndex, res.txAllOut)
				}
				validateTasks.pushPending(res.ver.TxnIndex)
				execTasks.markComplete(res.ver.TxnIndex)
				if diagExecSuccess[res.ver.TxnIndex] > 0 && diagExecAbort[res.ver.TxnIndex] == 0 {
					log.Debug("blockstm", "got multiple successful execution w/o abort?", "Tx", res.ver.TxnIndex, "incarnation", res.ver.Incarnation)
				}
				diagExecSuccess[res.ver.TxnIndex]++
				cntSuccess++
			}
		case ErrExecAbort:
			{
				// bit of a subtle / tricky bug here. this adds the tx back to pending ...
				execTasks.revertInProgress(res.ver.TxnIndex)
				// ... but the incarnation needs to be bumped
				txIncarnations[res.ver.TxnIndex]++
				diagExecAbort[res.ver.TxnIndex]++
				cntAbort++
			}
		default:
			{
				err = res.err
				break
			}
		}

		// if we got more work, queue one up...
		nextTx := execTasks.takeNextPending()
		if nextTx != -1 {
			cntExec++
			chTasks <- ExecVersionView{ver: Version{nextTx, txIncarnations[nextTx]}, et: tasks[nextTx], mvh: mvh}
		}

		// do validations ...
		maxComplete := execTasks.maxAllComplete()

		const validationIncrement = 2

		cntValidate := validateTasks.countPending()
		// if we're currently done with all execution tasks then let's validate everything; otherwise do one increment ...
		if execTasks.countComplete() != len(tasks) && cntValidate > validationIncrement {
			cntValidate = validationIncrement
		}

		var toValidate []int

		for i := 0; i < cntValidate; i++ {
			if validateTasks.minPending() <= maxComplete {
				toValidate = append(toValidate, validateTasks.takeNextPending())
			} else {
				break
			}
		}

		for i := 0; i < len(toValidate); i++ {
			cntTotalValidations++

			tx := toValidate[i]
			log.Debug("blockstm", "validating task", tx)

			if ValidateVersion(tx, lastTxIO, mvh) {
				log.Debug("blockstm", "* completed validation task", tx)
				validateTasks.markComplete(tx)
			} else {
				log.Debug("blockstm", "* validation task FAILED", tx)
				cntValidationFail++
				diagExecAbort[tx]++
				for _, v := range lastTxIO.AllWriteSet(tx) {
					mvh.MarkEstimate(v.Path, tx)
				}
				// 'create validation tasks for all transactions > tx ...'
				validateTasks.pushPendingSet(execTasks.getRevalidationRange(tx + 1))
				validateTasks.clearInProgress(tx) // clear in progress - pending will be added again once new incarnation executes
				if execTasks.checkPending(tx) {
					// println() // have to think about this ...
				} else {
					execTasks.pushPending(tx)
					execTasks.clearComplete(tx)
					txIncarnations[tx]++
				}
			}
		}

		// if we didn't queue work previously, do check again so we keep making progress ...
		if nextTx == -1 {
			nextTx = execTasks.takeNextPending()
			if nextTx != -1 {
				cntExec++

				log.Debug("blockstm", "# tx queued up", nextTx)
				chTasks <- ExecVersionView{ver: Version{nextTx, txIncarnations[nextTx]}, et: tasks[nextTx], mvh: mvh}
			}
		}

		if validateTasks.countComplete() == len(tasks) && execTasks.countComplete() == len(tasks) {
			log.Debug("blockstm exec summary", "execs", cntExec, "success", cntSuccess, "aborts", cntAbort, "validations", cntTotalValidations, "failures", cntValidationFail)
			break
		}
	}

	for i := 0; i < numGoProcs; i++ {
		chDone <- true
	}
	close(chTasks)
	close(chResults)

	return
}