/*
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// Out-of-date determination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"
)

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 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
}

func isBuiltNow(fdDep *os.File) (bool, *recfile.Reader, error) {
	r := recfile.NewReader(fdDep)
	m, err := r.NextMap()
	if err != nil {
		return false, nil, err
	}
	if m["Build"] == "" {
		return false, r, errors.New(".dep missing Build:")
	}
	return m["Build"] == BuildUUID, r, nil
}

func rebuildStamped(cwd, tgt, depPath string) (string, error) {
	relTgt, err := filepath.Rel(Cwd, path.Join(cwd, tgt))
	if err != nil {
		panic(err)
	}
	errs := make(chan error, 1)
	if err = runScript(relTgt, errs); err != nil {
		return "", err
	}
	if err = <-errs; !isOkRun(err) {
		return "", errors.New("build failed")
	}
	fdDep, err := os.Open(depPath)
	if err != nil {
		return "", err
	}
	defer fdDep.Close()
	builtNow, r, err := isBuiltNow(fdDep)
	if err != nil {
		return "", err
	}
	if !builtNow {
		return "", errors.New("is not built")
	}
	var stampTheir string
	for {
		m, err := r.NextMap()
		if err != nil {
			if err == io.EOF {
				break
			}
			return "", err
		}
		if m["Type"] == "stamp" {
			stampTheir = m["Hash"]
			break
		}
	}
	return stampTheir, nil
}

func isOOD(cwd, tgt string, level int) (bool, error) {
	tgtOrig := tgt
	indent := strings.Repeat(". ", level)
	trace(CDebug, "ood: %s%s checking", indent, tgtOrig)
	cwd, tgt = cwdAndTgt(path.Join(cwd, tgt))
	depPath := path.Join(cwd, RedoDir, tgt+DepSuffix)
	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()
	ood := false

	builtNow, r, err := isBuiltNow(fdDep)
	if err != nil {
		return true, TgtErr{tgtOrig, err}
	}
	if builtNow {
		trace(CDebug, "ood: %s%s -> already built", indent, tgtOrig)
		return false, nil
	}

	var stampOur string
	ifcreates := []map[string]string{}
	ifchanges := []map[string]string{}
	for {
		m, err := r.NextMap()
		if err != nil {
			if err == io.EOF {
				break
			}
			return true, TgtErr{tgtOrig, err}
		}
		switch m["Type"] {
		case "always":
			trace(CDebug, "ood: %s%s -> always", indent, tgtOrig)
			ood = true
		case "ifcreate":
			ifcreates = append(ifcreates, m)
		case "ifchange":
			ifchanges = append(ifchanges, m)
		case "stamp":
			stampOur = m["Hash"]
			trace(CDebug, "ood: %s%s -> stamped: %s", indent, tgtOrig, stampOur)
		default:
			return ood, TgtErr{tgtOrig, errors.New("invalid format of .dep")}
		}
	}
	if ood {
		goto StampCheck
	}

	for _, m := range ifcreates {
		theirTgt := m["Target"]
		if theirTgt == "" {
			return ood, TgtErr{tgtOrig, errors.New("invalid format of .dep")}
		}
		if _, err = os.Stat(path.Join(cwd, theirTgt)); err == nil {
			trace(CDebug, "ood: %s%s -> created", indent, tgtOrig)
			ood = true
			goto StampCheck
		}
	}

	for _, m := range 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()
		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)
		}
		fd.Close()
		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)
		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 && stampOur != "" {
		trace(CDebug, "ood: %s%s run, because stamped", indent, tgtOrig)
		stampTheir, err := rebuildStamped(cwd, tgt, depPath)
		if err != nil {
			return true, TgtErr{tgtOrig, err}
		}
		trace(CDebug, "ood: %s%s -> stamp: %s %s", indent, tgtOrig, stampOur, stampTheir)
		if stampOur == stampTheir {
			ood = false
		}
	}
	trace(CDebug, "ood: %s%s: %v", indent, tgtOrig, ood)
	return ood, nil
}