package analyze

import (
	"bytes"
	"fmt"
	"os/exec"
	"strings"

	"github.com/bazelbuild/buildtools/edit"
	"github.com/bazelbuild/rules_typescript/ts_auto_deps/workspace"
	"github.com/golang/protobuf/proto"

	appb "github.com/bazelbuild/buildtools/build_proto"
)

var (
	commonModuleLocations = []string{}

	ts_auto_depsManagedRuleClasses = []string{
		"ts_library",
		"ts_declaration",
		"ng_module",
		"js_library",
	}
)

// QueryBasedTargetLoader uses Bazel query to load targets from BUILD files.
type QueryBasedTargetLoader struct {
	workdir     string
	bazelBinary string
}

// NewQueryBasedTargetLoader constructs a new QueryBasedTargetLoader rooted
// in workdir.
func NewQueryBasedTargetLoader(workdir, bazelBinary string) *QueryBasedTargetLoader {
	return &QueryBasedTargetLoader{
		workdir:     workdir,
		bazelBinary: bazelBinary,
	}
}

// LoadLabels uses Bazel query to load targets associated with labels from BUILD
// files.
func (q *QueryBasedTargetLoader) LoadLabels(labels []string) (map[string]*appb.Rule, error) {
	// Ensure the labels are unique to minimize the total number of targets that
	// need to be loaded.
	r, err := q.batchQuery(dedupeLabels(labels))
	if err != nil {
		return nil, err
	}
	labelToRule := make(map[string]*appb.Rule)
	for _, target := range r.GetTarget() {
		label, err := q.ruleLabel(target)
		if err != nil {
			return nil, err
		}
		labelToRule[label] = target.GetRule()
	}
	return labelToRule, nil
}

// LoadImportPaths uses Bazel Query to load targets associated with import
// paths from BUILD files.
func (q *QueryBasedTargetLoader) LoadImportPaths(_ string, paths []string) (map[string]*appb.Rule, error) {
	var remainingImportPaths []string
	results := make(map[string]*appb.Rule)
	for _, path := range paths {
		if trim := strings.TrimPrefix(path, workspace.Name()+"/"); trim != path {
			// TODO(jdhamlik): Optimize by grouping the queries into one larger query.
			// TODO(jdhamlik): Handle .d.ts and .tsx files.
			r, err := q.query(trim + ".ts")
			if err != nil {
				return nil, err
			}
			targets := r.GetTarget()
			// Expecting to get one, and only one, target per query.
			n := len(targets)
			if n < 1 {
				return nil, fmt.Errorf("failed to resolved a target for file %q", trim+".ts")
			}
			if n > 1 {
				return nil, fmt.Errorf("got %d targets when only one was expected", n)
			}
			t, err := q.loadRuleIncludingFile(targets[0].GetSourceFile().GetName())
			if err != nil {
				return nil, err
			}
			results[path] = t
		} else if trim := strings.TrimPrefix(path, "goog:"); trim != path {
			// There are no current heuristics in this implementation for
			// 'goog:' imports. That is handled by the ts_auto_deps binary proper.
			results[path] = nil
		} else {
			// The import is not explicitly under google3 or a closure-style
			// import.
			remainingImportPaths = append(remainingImportPaths, path)
		}
	}
	var potentialCommonImports []string
	// Attempt to locate the file rooted in the workspace even though it isn't
	// prefixed by 'google3/'.
	for _, imp := range remainingImportPaths {
		// If the path has a suffix of ".ngfactory" or ".ngsummary", it might
		// be an Angular AOT generated file. We can infer the target as we
		// infer its corresponding ngmodule target by simply stripping the
		// ".ngfactory" / ".ngsummary" suffix
		path := strings.TrimSuffix(strings.TrimSuffix(imp, ".ngsummary"), ".ngfactory")
		res, err := q.batchQuery(pathWithExtensions(path))
		if err != nil {
			return nil, err
		}
		if len(res.GetTarget()) > 0 {
			target := res.GetTarget()[0]
			label, err := q.sourceFileLabel(target)
			if err != nil {
				return nil, err
			}
			rule, err := q.loadRuleIncludingFile(label)
			if err != nil {
				return nil, err
			}
			results[imp] = rule
			continue
		}
		potentialCommonImports = append(potentialCommonImports, imp)
	}
	if err := q.resolveImportsInCommonLocations(results, potentialCommonImports); err != nil {
		return nil, err
	}
	return results, nil
}

func (q *QueryBasedTargetLoader) ruleLabel(target *appb.Target) (string, error) {
	if t := target.GetType(); t != appb.Target_RULE {
		return "", fmt.Errorf("target contains object of type %q instead of type %q", t, appb.Target_RULE)
	}
	return target.GetRule().GetName(), nil
}

func (q *QueryBasedTargetLoader) sourceFileLabel(target *appb.Target) (string, error) {
	if t := target.GetType(); t != appb.Target_SOURCE_FILE {
		return "", fmt.Errorf("target contains object of type %q instead of type %q", t, appb.Target_SOURCE_FILE)
	}
	return target.GetSourceFile().GetName(), nil
}

// loadRuleIncludingFile loads the target associated with a file label.
func (q *QueryBasedTargetLoader) loadRuleIncludingFile(fileLabel string) (*appb.Rule, error) {
	_, pkg, file := edit.ParseLabel(fileLabel)
	// Filter the targets in the file label's package to only targets which
	// include the file in their 'srcs' attribute.
	r, err := q.query(fmt.Sprintf("attr('srcs', %s, //%s:*)", file, pkg))
	if err != nil {
		return nil, err
	}
	for _, target := range r.GetTarget() {
		rule := target.GetRule()
		for _, src := range listAttribute(rule, "srcs") {
			_, _, path := edit.ParseLabel(src)
			// Return the first rule which has a source file exactly matching
			// the requested file path.
			if path == file {
				return rule, nil
			}
		}
	}
	return nil, fmt.Errorf("failed to resolved a target for file label %q", fileLabel)
}

// searchCommonLocations searches through common locations like third_party to
// find a target providing imports which cannot be resolved using other
// techniques.
func (q *QueryBasedTargetLoader) resolveImportsInCommonLocations(results map[string]*appb.Rule, paths []string) error {
	var queries []string
	labelToPath := make(map[string]string)

	for _, path := range paths {
		// third_party uses '_' instead of '-' since the latter is not allowed
		// in target labels
		underscored := strings.Replace(path, "-", "_", -1)
		file := underscored
		module := underscored
		if i := strings.Index(underscored, "/"); i >= 0 {
			// Use the slash in the import path as a separator between the
			// module name and the path under the module.
			file = underscored[i+1:]
			module = commonModuleName(underscored[:i])
		}
		for _, l := range commonModuleLocations {
			// Construct the potential target label in the common location.
			target := fmt.Sprintf("%s:%s", fmt.Sprintf(l, module), file)
			queries = append(queries, target)
			labelToPath[target] = path
		}
	}
	r, err := q.batchQuery(queries)
	if err != nil {
		return err
	}
	for _, target := range r.GetTarget() {
		r := target.GetRule()
		// TODO(jdhamlik): Determine if it's required that the alias resolves to
		// an allowedRuleClass.
		// Allow alias rules to provide imports. Alias rules should only appear
		// in this context if they are special-cased above.
		if c := r.GetRuleClass(); isTazeManagedRuleClass(c) || c == "alias" {
			results[labelToPath[r.GetName()]] = r
		}
	}
	return nil
}

// batchQuery runs a set of queries with a single call to Bazel query and the
// '--keep_going' flag.
func (q *QueryBasedTargetLoader) batchQuery(queries []string) (*appb.QueryResult, error) {
	// Join all of the queries with a '+' character according to Bazel's
	// syntax for running multiple queries.
	return q.query("--keep_going", strings.Join(queries, "+"))
}

func (q *QueryBasedTargetLoader) query(args ...string) (*appb.QueryResult, error) {
	n := len(args)
	if n < 1 {
		return nil, fmt.Errorf("expected at least one argument")
	}
	if query := args[n-1]; query == "" {
		// An empty query was provided so return an empty result without
		// making a call to Bazel.
		return &appb.QueryResult{}, nil
	}
	var stdout, stderr bytes.Buffer
	args = append([]string{"query", "--output=proto"}, args...)
	cmd := exec.Command(q.bazelBinary, args...)
	cmd.Dir = q.workdir
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		// Exit status 3 is a direct result of one or more queries in a set of
		// queries not returning a result while running with the '--keep_going'
		// flag. Since one query failing to return a result does not hinder the
		// other queries from returning a result, ignore these errors.
		if err.Error() != "exit status 3" {
			// The error provided as a result is less useful than the contents of
			// stderr for debugging.
			return nil, fmt.Errorf(stderr.String())
		}
	}
	var result appb.QueryResult
	if err := proto.Unmarshal(stdout.Bytes(), &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// dedupeLabels returns a new set of labels with no duplicates.
func dedupeLabels(labels []string) []string {
	addedLabels := make(map[string]bool)
	var uniqueLabels []string
	for _, label := range labels {
		if _, added := addedLabels[label]; !added {
			addedLabels[label] = true
			uniqueLabels = append(uniqueLabels, label)
		}
	}
	return uniqueLabels
}

// commonModuleName maps module names to their common names. If no common name
// is set for a module, it returns the module's name as is.
func commonModuleName(path string) string {
	return path
}

// isTazeManagedRuleClass checks if a class is a ts_auto_deps-managed rule class.
func isTazeManagedRuleClass(class string) bool {
	for _, c := range ts_auto_depsManagedRuleClasses {
		if c == class {
			return true
		}
	}
	return false
}