// Copyright 2023 Harness, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package gitea

import (
	"context"
	"fmt"
	"io"
	"math"
	"strings"

	"github.com/harness/gitness/gitrpc/internal/types"

	gitea "code.gitea.io/gitea/modules/git"
	gitearef "code.gitea.io/gitea/modules/git/foreachref"
)

func DefaultInstructor(_ types.WalkReferencesEntry) (types.WalkInstruction, error) {
	return types.WalkInstructionHandle, nil
}

// WalkReferences uses the provided options to filter the available references of the repo,
// and calls the handle function for every matching node.
// The instructor & handler are called with a map that contains the matching value for every field provided in fields.
// TODO: walkGiteaReferences related code should be moved to separate file.
func (g Adapter) WalkReferences(ctx context.Context,
	repoPath string, handler types.WalkReferencesHandler, opts *types.WalkReferencesOptions) error {
	// backfil optional options
	if opts.Instructor == nil {
		opts.Instructor = DefaultInstructor
	}
	if len(opts.Fields) == 0 {
		opts.Fields = []types.GitReferenceField{types.GitReferenceFieldRefName, types.GitReferenceFieldObjectName}
	}
	if opts.MaxWalkDistance <= 0 {
		opts.MaxWalkDistance = math.MaxInt32
	}
	if opts.Patterns == nil {
		opts.Patterns = []string{}
	}
	if string(opts.Sort) == "" {
		opts.Sort = types.GitReferenceFieldRefName
	}

	// prepare for-each-ref input
	sortArg := mapToGiteaReferenceSortingArgument(opts.Sort, opts.Order)
	rawFields := make([]string, len(opts.Fields))
	for i := range opts.Fields {
		rawFields[i] = string(opts.Fields[i])
	}
	giteaFormat := gitearef.NewFormat(rawFields...)

	// initializer pipeline for output processing
	pipeOut, pipeIn := io.Pipe()
	defer pipeOut.Close()
	defer pipeIn.Close()
	stderr := strings.Builder{}
	rc := &gitea.RunOpts{Dir: repoPath, Stdout: pipeIn, Stderr: &stderr}

	go func() {
		// create array for args as patterns have to be passed as separate args.
		args := []string{
			"for-each-ref",
			"--format",
			giteaFormat.Flag(),
			"--sort",
			sortArg,
			"--count",
			fmt.Sprint(opts.MaxWalkDistance),
			// "--ignore-case" // slows down performance drastically
		}
		args = append(args, opts.Patterns...)
		err := gitea.NewCommand(ctx, args...).Run(rc)
		if err != nil {
			_ = pipeIn.CloseWithError(gitea.ConcatenateError(err, stderr.String()))
		} else {
			_ = pipeIn.Close()
		}
	}()

	// TODO: return error from git command!!!!

	parser := giteaFormat.Parser(pipeOut)
	return walkGiteaReferenceParser(parser, handler, opts)
}

func walkGiteaReferenceParser(parser *gitearef.Parser, handler types.WalkReferencesHandler,
	opts *types.WalkReferencesOptions) error {
	for i := int32(0); i < opts.MaxWalkDistance; i++ {
		// parse next line - nil if end of output reached or an error occurred.
		rawRef := parser.Next()
		if rawRef == nil {
			break
		}

		// convert to correct map.
		ref, err := mapGiteaRawRef(rawRef)
		if err != nil {
			return err
		}

		// check with the instructor on the next instruction.
		instruction, err := opts.Instructor(ref)
		if err != nil {
			return fmt.Errorf("error getting instruction: %w", err)
		}

		if instruction == types.WalkInstructionSkip {
			continue
		}
		if instruction == types.WalkInstructionStop {
			break
		}

		// otherwise handle the reference.
		err = handler(ref)
		if err != nil {
			return fmt.Errorf("error handling reference: %w", err)
		}
	}

	if err := parser.Err(); err != nil {
		return processGiteaErrorf(err, "failed to parse reference walk output")
	}

	return nil
}

// GetRef get's the target of a reference
// IMPORTANT provide full reference name to limit risk of collisions across reference types
// (e.g `refs/heads/main` instead of `main`).
func (g Adapter) GetRef(ctx context.Context, repoPath, reference string) (string, error) {
	cmd := gitea.NewCommand(ctx, "show-ref", "--verify", "-s", "--", reference)
	stdout, _, err := cmd.RunStdString(&gitea.RunOpts{
		Dir: repoPath,
	})
	if err != nil {
		if err.IsExitCode(128) && strings.Contains(err.Stderr(), "not a valid ref") {
			return "", types.ErrNotFound
		}
		return "", err
	}

	return strings.TrimSpace(stdout), nil
}

// UpdateRef allows to update / create / delete references
// IMPORTANT provide full reference name to limit risk of collisions across reference types
// (e.g `refs/heads/main` instead of `main`).
func (g Adapter) UpdateRef(ctx context.Context,
	repoPath, reference, newValue, oldValue string,
) error {
	args := make([]string, 0, 4)
	args = append(args, "update-ref")
	if newValue == "" {
		// if newvalue is empty, delete ref
		args = append(args, "-d", reference)
	} else {
		args = append(args, reference, newValue)
	}

	// if an old value was provided, verify it matches.
	if oldValue != "" {
		args = append(args, oldValue)
	}

	cmd := gitea.NewCommand(ctx, args...)
	_, _, err := cmd.RunStdString(&gitea.RunOpts{
		Dir: repoPath,
	})
	if err != nil {
		return processGiteaErrorf(err, "update-ref failed")
	}

	return nil
}