// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package govulncheck

import (
	"strings"

	"golang.org/x/mod/semver"
	"golang.org/x/vuln/internal"
	"golang.org/x/vuln/internal/result"
	isem "golang.org/x/vuln/internal/semver"
	"golang.org/x/vuln/internal/vulncheck"
	"golang.org/x/vuln/osv"
)

// latestFixed returns the latest fixed version in the list of affected ranges,
// or the empty string if there are no fixed versions.
func latestFixed(as []osv.Affected) string {
	v := ""
	for _, a := range as {
		for _, r := range a.Ranges {
			if r.Type == osv.TypeSemver {
				for _, e := range r.Events {
					if e.Fixed != "" && (v == "" ||
						semver.Compare(isem.CanonicalizeSemverPrefix(e.Fixed), isem.CanonicalizeSemverPrefix(v)) > 0) {
						v = e.Fixed
					}
				}
			}
		}
	}
	return v
}

func foundVersion(modulePath string, moduleVersions map[string]string) string {
	var found string
	if v := moduleVersions[modulePath]; v != "" {
		found = versionString(modulePath, v[1:])
	}
	return found
}

func fixedVersion(modulePath string, affected []osv.Affected) string {
	fixed := latestFixed(affected)
	if fixed != "" {
		fixed = versionString(modulePath, fixed)
	}
	return fixed
}

// versionString prepends a version string prefix (`v` or `go`
// depending on the modulePath) to the given semver-style version string.
func versionString(modulePath, version string) string {
	if version == "" {
		return ""
	}
	v := "v" + version
	if modulePath == internal.GoStdModulePath || modulePath == internal.GoCmdModulePath {
		return semverToGoTag(v)
	}
	return v
}

// highest returns the highest (one with the smallest index) entry in the call
// stack for which f returns true.
func highest(cs []*result.StackFrame, f func(e *result.StackFrame) bool) int {
	for i := 0; i < len(cs); i++ {
		if f(cs[i]) {
			return i
		}
	}
	return -1
}

// lowest returns the lowest (one with the largest index) entry in the call
// stack for which f returns true.
func lowest(cs []*result.StackFrame, f func(e *result.StackFrame) bool) int {
	for i := len(cs) - 1; i >= 0; i-- {
		if f(cs[i]) {
			return i
		}
	}
	return -1
}

// pkgPath returns the package path from fn.
func pkgPath(fn *vulncheck.FuncNode) string {
	if fn.PkgPath != "" {
		return fn.PkgPath
	}
	s := strings.TrimPrefix(fn.RecvType, "*")
	if i := strings.LastIndexByte(s, '.'); i > 0 {
		s = s[:i]
	}
	return s
}

// moduleVersionMap builds a map from module paths to versions.
func moduleVersionMap(mods []*vulncheck.Module) map[string]string {
	moduleVersions := map[string]string{}
	for _, m := range mods {
		v := m.Version
		if m.Replace != nil {
			v = m.Replace.Version
		}
		moduleVersions[m.Path] = v
	}
	return moduleVersions
}

// pkgMap creates a map from package paths to packages for all pkgs
// and their transitive imports.
func pkgMap(pkgs []*vulncheck.Package) map[string]*vulncheck.Package {
	m := make(map[string]*vulncheck.Package)
	var visit func(*vulncheck.Package)
	visit = func(p *vulncheck.Package) {
		if _, ok := m[p.PkgPath]; ok {
			return
		}
		m[p.PkgPath] = p

		for _, i := range p.Imports {
			visit(i)
		}
	}

	for _, p := range pkgs {
		visit(p)
	}
	return m
}