/*
goredo -- redo implementation on pure Go
Copyright (C) 2020 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

// Out-of-date determination

package main

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path"
	"path/filepath"
	"strings"

	"go.cypherpunks.ru/recfile"
)

const (
	DepTypeIfcreate = "ifcreate"
	DepTypeIfchange = "ifchange"
	DepTypeAlways   = "always"
	DepTypeStamp    = "stamp"
)

type TgtErr struct {
	Tgt string
	Err error
}

func (e TgtErr) Unwrap() error { return e.Err }

func (e TgtErr) Error() string {
	return fmt.Sprintf("%s: %s", e.Tgt, e.Err)
}

func cwdMustRel(paths ...string) string {
	rel, err := filepath.Rel(Cwd, path.Join(paths...))
	if err != nil {
		panic(err)
	}
	return rel
}

func cwdAndTgt(tgt string) (string, string) {
	cwd, tgt := path.Split(tgt)
	cwd, err := filepath.Abs(cwd)
	if err != nil {
		panic(err)
	}
	return cwd, tgt
}

func isSrc(cwd, tgt string) bool {
	d, f := path.Split(path.Join(cwd, tgt))
	if _, err := os.Stat(path.Join(d, f)); err != nil {
		return false
	}
	if _, err := os.Stat(path.Join(d, RedoDir, f+DepSuffix)); err == nil {
		return false
	}
	return true
}

type DepInfo struct {
	build     string
	always    bool
	stamp     string
	stampSame bool
	ifcreates []string
	ifchanges []map[string]string
}

func depRead(fdDep *os.File) (*DepInfo, error) {
	r := recfile.NewReader(fdDep)
	m, err := r.NextMap()
	if err != nil {
		return nil, err
	}
	depInfo := DepInfo{}
	if b := m["Build"]; b == "" {
		return nil, errors.New(".dep missing Build:")
	} else {
		depInfo.build = b
	}
	for {
		m, err := r.NextMap()
		if err != nil {
			if err == io.EOF {
				break
			}
			return nil, err
		}
		switch m["Type"] {
		case DepTypeAlways:
			depInfo.always = true
		case DepTypeIfcreate:
			dep := m["Target"]
			if dep == "" {
				return nil, errors.New("invalid format of .dep")
			}
			depInfo.ifcreates = append(depInfo.ifcreates, dep)
		case DepTypeIfchange:
			delete(m, "Type")
			depInfo.ifchanges = append(depInfo.ifchanges, m)
		case DepTypeStamp:
			hsh := m["Hash"]
			if hsh == "" {
				return nil, errors.New("invalid format of .dep")
			}
			depInfo.stamp = hsh
			depInfo.stampSame = m["Same"] == "true"
		default:
			return nil, errors.New("invalid format of .dep")
		}
	}
	return &depInfo, nil
}

func rebuildStamped(cwd, tgt, depPath, stampPrev string) (bool, error) {
	relTgt := cwdMustRel(cwd, tgt)
	errs := make(chan error, 1)
	if err := runScript(relTgt, errs, stampPrev); err != nil {
		return false, err
	}
	if err := <-errs; !isOkRun(err) {
		return false, errors.New("build failed")
	}
	fdDep, err := os.Open(depPath)
	if err != nil {
		return false, err
	}
	defer fdDep.Close()
	depInfo, err := depRead(fdDep)
	if err != nil {
		return false, err
	}
	if depInfo.build != BuildUUID {
		return false, errors.New("is not built")
	}
	return depInfo.stampSame, nil
}

func formDepPath(cwd, tgt string) string {
	cwd, tgt = cwdAndTgt(path.Join(cwd, tgt))
	return path.Join(cwd, RedoDir, tgt+DepSuffix)
}

func isOOD(cwd, tgtOrig string, level int, depInfo *DepInfo) (bool, error) {
	indent := strings.Repeat(". ", level)
	trace(CDebug, "ood: %s%s checking", indent, tgtOrig)
	cwd, tgt := cwdAndTgt(path.Join(cwd, tgtOrig))
	depPath := formDepPath(cwd, tgt)
	if depInfo == nil {
		fdDep, err := os.Open(depPath)
		if err != nil {
			trace(CDebug, "ood: %s%s -> no dep: %s", indent, tgtOrig, depPath)
			return true, nil
		}
		defer fdDep.Close()
		depInfo, err = depRead(fdDep)
		if err != nil {
			return true, TgtErr{tgtOrig, err}
		}
	}

	if depInfo.build == BuildUUID {
		trace(CDebug, "ood: %s%s -> already built", indent, tgtOrig)
		return false, nil
	}
	ood := depInfo.always
	if ood {
		goto StampCheck
	}

	for _, dep := range depInfo.ifcreates {
		if _, err := os.Stat(path.Join(cwd, dep)); err == nil {
			trace(CDebug, "ood: %s%s -> %s created", indent, tgtOrig, dep)
			ood = true
			goto StampCheck
		}
	}

	for _, m := range depInfo.ifchanges {
		dep := m["Target"]
		theirTs := m["Ctime"]
		theirHsh := m["Hash"]
		if dep == "" || theirTs == "" {
			return ood, TgtErr{tgtOrig, errors.New("invalid format of .dep")}
		}
		trace(CDebug, "ood: %s%s -> %s: checking", indent, tgtOrig, dep)

		fd, err := os.Open(path.Join(cwd, dep))
		if err != nil {
			if os.IsNotExist(err) {
				trace(CDebug, "ood: %s%s -> %s: not exists", indent, tgtOrig, dep)
				ood = true
				goto StampCheck
			}
			return ood, TgtErr{tgtOrig, err}
		}
		defer fd.Close()

		var depDepInfo *DepInfo
		if !(dep == tgt || isSrc(cwd, dep)) {
			trace(CDebug, "ood: %s%s -> %s: prereading .dep", indent, tgtOrig, dep)
			depFdDep, err := os.Open(formDepPath(cwd, dep))
			if err != nil {
				return ood, TgtErr{path.Join(tgtOrig, dep), err}
			}
			defer depFdDep.Close()
			depDepInfo, err = depRead(depFdDep)
			if err != nil {
				return ood, TgtErr{path.Join(tgtOrig, dep), err}
			}
		}

		if depDepInfo != nil && depDepInfo.build == BuildUUID {
			trace(
				CDebug, "ood: %s%s -> %s: .dep says build is same",
				indent, tgtOrig, dep,
			)
			if !depDepInfo.stampSame {
				trace(
					CDebug, "ood: %s%s -> %s: .dep says stamp is not same",
					indent, tgtOrig, dep,
				)
				ood = true
				return ood, nil
			}
			trace(
				CDebug, "ood: %s%s -> %s: .dep says stamp is same",
				indent, tgtOrig, dep,
			)
			continue
		}

		if depDepInfo == nil || !depDepInfo.always && depDepInfo.stamp == "" {
			ts, err := fileCtime(fd)
			if err != nil {
				return ood, TgtErr{tgtOrig, err}
			}
			if theirTs == ts {
				trace(CDebug, "ood: %s%s -> %s: same ctime", indent, tgtOrig, dep)
			} else if NoHash || theirHsh == "" {
				trace(CDebug, "ood: %s%s -> %s: ctime differs", indent, tgtOrig, dep)
				ood = true
				goto StampCheck
			} else {
				hsh, err := fileHash(fd)
				if err != nil {
					return ood, TgtErr{tgtOrig, err}
				}
				if theirHsh != hsh {
					trace(CDebug, "ood: %s%s -> %s: hash differs", indent, tgtOrig, dep)
					ood = true
					goto StampCheck
				}
				trace(CDebug, "ood: %s%s -> %s: same hash", indent, tgtOrig, dep)
			}
		}

		if dep == tgt {
			trace(CDebug, "ood: %s%s -> %s: same target", indent, tgtOrig, dep)
			continue
		}
		if isSrc(cwd, dep) {
			trace(CDebug, "ood: %s%s -> %s: is source", indent, tgtOrig, dep)
			continue
		}

		depOod, err := isOOD(cwd, dep, level+1, depDepInfo)
		if err != nil {
			return ood, TgtErr{tgtOrig, err}
		}
		if depOod {
			trace(CDebug, "ood: %s%s -> %s: ood", indent, tgtOrig, dep)
			ood = true
			goto StampCheck
		}
		trace(CDebug, "ood: %s%s -> %s: !ood", indent, tgtOrig, dep)
	}

StampCheck:
	if ood && depInfo.stamp != "" {
		trace(CDebug, "ood: %s%s run, because stamped", indent, tgtOrig)
		stampSame, err := rebuildStamped(cwd, tgt, depPath, depInfo.stamp)
		if err != nil {
			return true, TgtErr{tgtOrig, err}
		}
		trace(CDebug, "ood: %s%s -> stamp: same: %v", indent, tgtOrig, stampSame)
		ood = !stampSame
	}
	trace(CDebug, "ood: %s%s: %v", indent, tgtOrig, ood)
	return ood, nil
}