// Copyright 2022 Harness Inc. All rights reserved.
// Use of this source code is governed by the Polyform Free Trial License
// that can be found in the LICENSE.md file for this repository.

package gitea

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"strconv"
	"strings"

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

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

const (
	giteaPrettyLogFormat = `--pretty=format:%H`
)

// GetLatestCommit gets the latest commit of a path relative from the provided reference.
// Note: ref can be Branch / Tag / CommitSHA.
func (g Adapter) GetLatestCommit(ctx context.Context, repoPath string,
	ref string, treePath string) (*types.Commit, error) {
	treePath = cleanTreePath(treePath)

	giteaRepo, err := gitea.OpenRepository(ctx, repoPath)
	if err != nil {
		return nil, err
	}
	defer giteaRepo.Close()

	giteaCommit, err := giteaGetCommitByPath(giteaRepo, ref, treePath)
	if err != nil {
		return nil, processGiteaErrorf(err, "error getting latest commit for '%s'", treePath)
	}

	return mapGiteaCommit(giteaCommit)
}

// giteaGetCommitByPath is a copy of gitea code - required as we want latest commit per specific branch.
func giteaGetCommitByPath(giteaRepo *gitea.Repository, ref string, treePath string) (*gitea.Commit, error) {
	if treePath == "" {
		treePath = "."
	}

	// NOTE: the difference to gitea implementation is passing `ref`.
	stdout, _, runErr := gitea.NewCommand(giteaRepo.Ctx, "log", ref, "-1", giteaPrettyLogFormat, "--", treePath).
		RunStdBytes(&gitea.RunOpts{Dir: giteaRepo.Path})
	if runErr != nil {
		return nil, fmt.Errorf("failed to trigger log command: %w", runErr)
	}

	giteaCommits, err := giteaParsePrettyFormatLogToList(giteaRepo, stdout)
	if err != nil {
		return nil, err
	}

	return giteaCommits[0], nil
}

// giteaParsePrettyFormatLogToList is an exact copy of gitea code.
func giteaParsePrettyFormatLogToList(giteaRepo *gitea.Repository, logs []byte) ([]*gitea.Commit, error) {
	var giteaCommits []*gitea.Commit
	if len(logs) == 0 {
		return giteaCommits, nil
	}

	parts := bytes.Split(logs, []byte{'\n'})

	for _, commitID := range parts {
		commit, err := giteaRepo.GetCommit(string(commitID))
		if err != nil {
			return nil, fmt.Errorf("failed to get commit '%s': %w", string(commitID), err)
		}
		giteaCommits = append(giteaCommits, commit)
	}

	return giteaCommits, nil
}

// ListCommits lists the commits reachable from ref.
// Note: ref can be Branch / Tag / CommitSHA.
func (g Adapter) ListCommits(ctx context.Context, repoPath string,
	ref string, page int, pageSize int) ([]types.Commit, int64, error) {
	giteaRepo, err := gitea.OpenRepository(ctx, repoPath)
	if err != nil {
		return nil, 0, err
	}
	defer giteaRepo.Close()

	// Get the giteaTopCommit object for the ref
	giteaTopCommit, err := giteaRepo.GetCommit(ref)
	if err != nil {
		return nil, 0, processGiteaErrorf(err, "error getting commit top commit for ref '%s'", ref)
	}

	giteaCommits, err := giteaTopCommit.CommitsByRange(page, pageSize)
	if err != nil {
		return nil, 0, processGiteaErrorf(err, "error getting commits")
	}

	totalCount, err := giteaTopCommit.CommitsCount()
	if err != nil {
		return nil, 0, processGiteaErrorf(err, "error getting total commit count")
	}

	commits := make([]types.Commit, len(giteaCommits))
	for i := range giteaCommits {
		var commit *types.Commit
		commit, err = mapGiteaCommit(giteaCommits[i])
		if err != nil {
			return nil, 0, err
		}
		commits[i] = *commit
	}

	// TODO: save to cast to int from int64, or we expect exceeding int.MaxValue?
	return commits, totalCount, nil
}

// GetCommit returns the (latest) commit for a specific ref.
// Note: ref can be Branch / Tag / CommitSHA.
func (g Adapter) GetCommit(ctx context.Context, repoPath string, ref string) (*types.Commit, error) {
	giteaRepo, err := gitea.OpenRepository(ctx, repoPath)
	if err != nil {
		return nil, err
	}
	defer giteaRepo.Close()

	commit, err := giteaRepo.GetCommit(ref)
	if err != nil {
		return nil, processGiteaErrorf(err, "error getting commit for ref '%s'", ref)
	}

	return mapGiteaCommit(commit)
}

// GetCommits returns the (latest) commits for a specific list of refs.
// Note: ref can be Branch / Tag / CommitSHA.
func (g Adapter) GetCommits(ctx context.Context, repoPath string, refs []string) ([]types.Commit, error) {
	giteaRepo, err := gitea.OpenRepository(ctx, repoPath)
	if err != nil {
		return nil, err
	}
	defer giteaRepo.Close()

	commits := make([]types.Commit, len(refs))
	for i, sha := range refs {
		var giteaCommit *gitea.Commit
		giteaCommit, err = giteaRepo.GetCommit(sha)
		if err != nil {
			return nil, processGiteaErrorf(err, "error getting commit '%s'", sha)
		}

		var commit *types.Commit
		commit, err = mapGiteaCommit(giteaCommit)
		if err != nil {
			return nil, err
		}
		commits[i] = *commit
	}

	return commits, nil
}

// GetCommitDivergences returns the count of the diverging commits for all branch pairs.
// IMPORTANT: If a max is provided it limits the overal count of diverging commits
// (max 10 could lead to (0, 10) while it's actually (2, 12)).
func (g Adapter) GetCommitDivergences(ctx context.Context, repoPath string,
	requests []types.CommitDivergenceRequest, max int32) ([]types.CommitDivergence, error) {
	var err error
	res := make([]types.CommitDivergence, len(requests))
	for i, req := range requests {
		res[i], err = g.getCommitDivergence(ctx, repoPath, req, max)
		if errors.Is(err, types.ErrNotFound) {
			res[i] = types.CommitDivergence{Ahead: -1, Behind: -1}
			continue
		}
		if err != nil {
			return nil, err
		}
	}

	return res, nil
}

// getCommitDivergence returns the count of diverging commits for a pair of branches.
// IMPORTANT: If a max is provided it limits the overal count of diverging commits
// (max 10 could lead to (0, 10) while it's actually (2, 12)).
// NOTE: Gitea implementation makes two git cli calls, but it can be done with one
// (downside is the max behavior explained above).
func (g Adapter) getCommitDivergence(ctx context.Context, repoPath string,
	req types.CommitDivergenceRequest, max int32) (types.CommitDivergence, error) {
	// prepare args
	args := []string{
		"rev-list",
		"--count",
		"--left-right",
	}
	// limit count if requested.
	if max > 0 {
		args = append(args, "--max-count")
		args = append(args, fmt.Sprint(max))
	}
	// add query to get commits without shared base commits
	args = append(args, fmt.Sprintf("%s...%s", req.From, req.To))

	var err error
	cmd := gitea.NewCommand(ctx, args...)
	stdOut, stdErr, err := cmd.RunStdString(&gitea.RunOpts{Dir: repoPath})
	if err != nil {
		return types.CommitDivergence{},
			processGiteaErrorf(err, "git rev-list failed for '%s...%s' (stdErr: '%s')", req.From, req.To, stdErr)
	}

	// parse output, e.g.: `1       2\n`
	rawLeft, rawRight, ok := strings.Cut(stdOut, "\t")
	if !ok {
		return types.CommitDivergence{}, fmt.Errorf("git rev-list returned unexpected output '%s'", stdOut)
	}

	// trim any unnecessary characters
	rawLeft = strings.TrimRight(rawLeft, " \t")
	rawRight = strings.TrimRight(rawRight, " \t\n")

	// parse numbers
	left, err := strconv.ParseInt(rawLeft, 10, 32)
	if err != nil {
		return types.CommitDivergence{},
			fmt.Errorf("failed to parse git rev-list output for ahead '%s' (full: '%s')): %w", rawLeft, stdOut, err)
	}
	right, err := strconv.ParseInt(rawRight, 10, 32)
	if err != nil {
		return types.CommitDivergence{},
			fmt.Errorf("failed to parse git rev-list output for behind '%s' (full: '%s')): %w", rawRight, stdOut, err)
	}

	return types.CommitDivergence{
		Ahead:  int32(left),
		Behind: int32(right),
	}, nil
}