package main

// What the keeper reads from the machine into the bus (novox/hq ADR 0507 §2, §4, §7): the local package
// database (`pacman -Q`, `pacman -Qeq`) with each package's repository from the sync databases (`pacman -Sl`),
// and what a full upgrade would change (`checkupdates`). Every line is read against the shape of a package name
// and a version, and a line that is not one is left out, so nothing but names, versions and repositories ever
// reaches a value on the bus (ADR 0507 §1): never a command line, an environment or a message pacman printed.
// None of these commands names a package, so none names a foreign one either.

import (
	"fmt"
	"regexp"
	"sort"
	"strings"
)

var (
	// packageName is what pacman allows in a package's name (makepkg's lint: alphanumerics and @._+-).
	packageName = regexp.MustCompile(`^[a-z0-9@._+][a-z0-9@._+-]*$`)
	// packageVersion is an epoch, a version and a release: alphanumerics and ._+:~-.
	packageVersion = regexp.MustCompile(`^[A-Za-z0-9._+~][A-Za-z0-9._+:~-]*$`)
	// repoName is a repository's section name in pacman.conf.
	repoName = regexp.MustCompile(`^[A-Za-z0-9_-][A-Za-z0-9._-]*$`)
)

// nameVersion reads a `<name> <version>` line, refusing anything else.
func nameVersion(l string) (string, string, bool) {
	f := strings.Fields(l)
	if len(f) != 2 || !packageName.MatchString(f[0]) || !packageVersion.MatchString(f[1]) {
		return "", "", false
	}
	return f[0], f[1], true
}

// ReadInstalled is the node's installed packages, sorted by name, each with its version, whether it was installed
// explicitly, and its repository or RepoForeign; and how many lines of pacman's output were not a package and
// were left out.
func (m *Machine) ReadInstalled() ([]InstalledPackage, int, error) {
	all, err := m.Out("pacman", "-Q")
	if err != nil {
		return nil, 0, err
	}
	explicit, err := m.query("-Qeq")
	if err != nil {
		return nil, 0, err
	}
	synced, err := m.Out("pacman", "-Sl")
	if err != nil {
		return nil, 0, err
	}
	skipped := 0
	ex := map[string]bool{}
	for _, l := range lines(explicit) {
		if n := strings.TrimSpace(l); packageName.MatchString(n) {
			ex[n] = true
		}
	}
	// A package in two repositories is the first's: `pacman -Sl` lists them in pacman.conf's order.
	repo := map[string]string{}
	for _, l := range lines(synced) {
		f := strings.Fields(l)
		if len(f) < 3 || !repoName.MatchString(f[0]) || !packageName.MatchString(f[1]) {
			continue
		}
		if _, seen := repo[f[1]]; !seen {
			repo[f[1]] = f[0]
		}
	}
	pkgs := []InstalledPackage{}
	for _, l := range lines(all) {
		name, version, ok := nameVersion(l)
		if !ok {
			skipped++
			continue
		}
		p := InstalledPackage{Name: name, Version: version, Explicit: ex[name], Repo: repo[name]}
		if p.Repo == "" {
			p.Repo = RepoForeign
		}
		pkgs = append(pkgs, p)
	}
	sort.Slice(pkgs, func(i, j int) bool { return pkgs[i].Name < pkgs[j].Name })
	return pkgs, skipped, nil
}

var updateLine = regexp.MustCompile(`^(\S+) (\S+) -> (\S+)$`)

// UpdateList is what a full upgrade would change, sorted by name, from checkupdates: a copy of the sync
// databases refreshed apart from the machine's own, so asking never makes a partial upgrade possible. Its
// status 2 is nothing to do; any other failure is an error, never an empty list.
func (m *Machine) UpdateList() ([]VersionChange, error) {
	r := m.Run(bg(), "checkupdates")
	switch {
	case r.Err == "ENOENT":
		return nil, fmt.Errorf("checkupdates is not installed: it comes with pacman-contrib, which this module declares")
	case r.Err == "" && r.Status == 2:
		return []VersionChange{}, nil
	case r.Err != "" || r.Status != 0:
		return nil, failure("checkupdates", "checkupdates", r)
	}
	ups := []VersionChange{}
	for _, l := range lines(r.Stdout) {
		u := updateLine.FindStringSubmatch(strings.TrimSpace(l))
		if u == nil || !packageName.MatchString(u[1]) || !packageVersion.MatchString(u[2]) || !packageVersion.MatchString(u[3]) {
			continue
		}
		ups = append(ups, VersionChange{Name: u[1], From: u[2], To: u[3]})
	}
	sort.Slice(ups, func(i, j int) bool { return ups[i].Name < ups[j].Name })
	return ups, nil
}

// DiffInstalled is what changed from one package list to the next, each list sorted by name: a package added,
// removed, or at another version. A change of reason or repository alone is no change of a version.
func DiffInstalled(before, after []InstalledPackage) Changes {
	c := Changes{Added: []PackageVersion{}, Removed: []PackageVersion{}, Changed: []VersionChange{}}
	was := map[string]string{}
	for _, p := range before {
		was[p.Name] = p.Version
	}
	is := map[string]bool{}
	for _, p := range after {
		is[p.Name] = true
		v, ok := was[p.Name]
		switch {
		case !ok:
			c.Added = append(c.Added, PackageVersion{p.Name, p.Version})
		case v != p.Version:
			c.Changed = append(c.Changed, VersionChange{p.Name, v, p.Version})
		}
	}
	for _, p := range before {
		if !is[p.Name] {
			c.Removed = append(c.Removed, PackageVersion{p.Name, p.Version})
		}
	}
	sort.Slice(c.Added, func(i, j int) bool { return c.Added[i].Name < c.Added[j].Name })
	sort.Slice(c.Removed, func(i, j int) bool { return c.Removed[i].Name < c.Removed[j].Name })
	sort.Slice(c.Changed, func(i, j int) bool { return c.Changed[i].Name < c.Changed[j].Name })
	return c
}

// Empty says a change changed nothing.
func (c Changes) Empty() bool { return len(c.Added)+len(c.Removed)+len(c.Changed) == 0 }