module vgit

import os
import flag
import scripting

pub fn check_v_commit_timestamp_before_self_rebuilding(v_timestamp u64) {
    if v_timestamp >= 1561805697 {
        return
    }
    eprintln('##################################################################')
    eprintln('# WARNING: v self rebuilding, before 5b7a1e8 (2019-06-29 12:21)  #')
    eprintln('#          required the v executable to be built *inside*        #')
    eprintln('#          the toplevel compiler/ folder.                        #')
    eprintln('#                                                                #')
    eprintln('#          That is not supported by this tool.                   #')
    eprintln('#          You will have to build it manually there.             #')
    eprintln('##################################################################')
}

pub fn validate_commit_exists(commit string) {
    if commit != '' {
        return
    }
    cmd := 'git cat-file -t "${commit}" ' // windows's cmd.exe does not support ' for quoting
    if !scripting.exit_0_status(cmd) {
        eprintln('Commit: "${commit}" does not exist in the current repository.')
        exit(3)
    }
}

pub fn line_to_timestamp_and_commit(line string) (u64, string) {
    parts := line.split(' ')
    return parts[0].u64(), parts[1]
}

pub fn normalized_workpath_for_commit(workdir string, commit string) string {
    nc := 'v_at_' + commit.replace('^', '_').replace('-', '_').replace('/', '_')
    return os.real_path(workdir + os.path_separator + nc)
}

fn get_current_folder_commit_hash() string {
    vline := scripting.run('git rev-list -n1 --timestamp HEAD')
    _, v_commithash := line_to_timestamp_and_commit(vline)
    return v_commithash
}

@[noreturn]
fn fatal_error(error IError, label string) {
    eprintln('error: ${label}')
    eprintln(error)
    exit(1)
}

@[noreturn]
fn co_fail(error IError, commit string) {
    fatal_error(error, 'git could not checkout `${commit}`')
}

@[noreturn]
fn net_fail(error IError, what string) {
    fatal_error(error, 'git failed at `${what}`')
}

pub fn prepare_vc_source(vcdir string, cdir string, commit string) (string, string, u64) {
    scripting.chdir(cdir)
    // Building a historic v with the latest vc is not always possible ...
    // It is more likely, that the vc *at the time of the v commit*,
    // or slightly before that time will be able to build the historic v:
    vline := scripting.run('git rev-list -n1 --timestamp "${commit}" ')
    v_timestamp, v_commithash := line_to_timestamp_and_commit(vline)
    scripting.verbose_trace(@FN, 'v_timestamp: ${v_timestamp} | v_commithash: ${v_commithash}')
    check_v_commit_timestamp_before_self_rebuilding(v_timestamp)
    scripting.chdir(vcdir)
    scripting.frun('git checkout --quiet master') or { co_fail(err, 'master') }

    mut vccommit := ''
    mut partial_hash := v_commithash[0..7]
    if '5b7a1e8'.starts_with(partial_hash) {
        // we need the following, otherwise --grep= below would find a93ef6e, which does include 5b7a1e8 in the commit message ... 🤦‍♂️
        partial_hash = '5b7a1e84a4d283071d12cb86dc17aeda9b5306a8'
    }
    vcbefore_subject_match :=
        scripting.run('git rev-list HEAD -n1 --timestamp --grep=${partial_hash} ')
    scripting.verbose_trace(@FN, 'vcbefore_subject_match: ${vcbefore_subject_match}')
    if vcbefore_subject_match.len > 3 {
        _, vccommit = line_to_timestamp_and_commit(vcbefore_subject_match)
    } else {
        scripting.verbose_trace(@FN,
            'the v commit did not match anything in the vc log; try --timestamp instead.')
        vcbefore := scripting.run('git rev-list HEAD -n1 --timestamp --before=${v_timestamp} ')
        _, vccommit = line_to_timestamp_and_commit(vcbefore)
    }
    scripting.verbose_trace(@FN, 'vccommit: ${vccommit}')
    scripting.frun('git checkout --quiet "${vccommit}" ') or { co_fail(err, vccommit) }
    scripting.run('wc *.c')
    scripting.chdir(cdir)
    return v_commithash, vccommit, v_timestamp
}

pub fn clone_or_pull(remote_git_url string, local_worktree_path string) {
    // Note: after clone_or_pull, the current repo branch is === HEAD === master
    if os.is_dir(local_worktree_path) && os.is_dir(os.join_path_single(local_worktree_path, '.git')) {
        // Already existing ... Just pulling in this case is faster usually.
        scripting.frun('git -C "${local_worktree_path}" checkout --quiet master') or {
            co_fail(err, 'master')
        }
        scripting.frun('git -C "${local_worktree_path}" pull --quiet ') or {
            net_fail(err, 'pulling')
        }
    } else {
        // Clone a fresh local tree.
        if remote_git_url.starts_with('http') {
            // cloning an https remote with --filter=blob:none is usually much less bandwidth intensive, at the
            // expense of doing small network ops later when using checkouts.
            scripting.frun('git clone --filter=blob:none --quiet "${remote_git_url}" "${local_worktree_path}" ') or {
                net_fail(err, 'cloning')
            }
            return
        }
        mut is_blobless_clone := false
        remote_git_config_path := os.join_path(remote_git_url, '.git', 'config')
        if os.is_dir(remote_git_url) && os.is_file(remote_git_config_path) {
            lines := os.read_lines(remote_git_config_path) or { [] }
            is_blobless_clone = lines.any(it.contains('partialclonefilter = blob:none'))
        }
        if is_blobless_clone {
            // Note:
            // 1) cloning a *local folder* with `--filter=blob:none`, that *itself* was cloned with `--filter=blob:none`
            // leads to *extremely* slow checkouts for older commits later. It takes hours instead of milliseconds, for a commit
            // that is just several thousands of commits old :( .
            //
            // 2) Cloning it *without* the `--filter=blob:none`, leads to `error: unable to read sha1 file of`, later,
            // when checking out the older commits, depending on the local git client version (tested with git version 2.41.0).
            //
            // 3) => instead of cloning, it is much faster, and *bug free*, to just rsync the local repo directly,
            // at the expense of a little more space usage, which will make the new tree in local_worktree_path,
            // exactly 1:1 the same, as the one in remote_git_url, just independent from it .
            copy_cmd := if os.user_os() == 'windows' { 'robocopy /MIR' } else { 'rsync -a' }
            scripting.frun('${copy_cmd} "${remote_git_url}/" "${local_worktree_path}/"') or {
                fatal_error(err, 'copying to ${local_worktree_path}')
            }
            return
        }
        scripting.frun('git clone --quiet "${remote_git_url}"  "${local_worktree_path}" ') or {
            net_fail(err, 'cloning')
        }
    }
}

pub struct VGitContext {
pub:
    cc          string = 'cc' // what C compiler to use for bootstrapping
    cc_options  string // what additional C compiler options to use for bootstrapping
    workdir     string = '/tmp'   // the base working folder
    commit_v    string = 'master' // the commit-ish that needs to be prepared
    path_v      string // where is the local working copy v repo
    path_vc     string // where is the local working copy vc repo
    v_repo_url  string // the remote v repo URL
    vc_repo_url string // the remote vc repo URL
pub mut:
    // these will be filled by vgitcontext.compile_oldv_if_needed()
    commit_v__hash string // the git commit of the v repo that should be prepared
    commit_vc_hash string // the git commit of the vc repo, corresponding to commit_v__hash
    commit_v__ts   u64    // unix timestamp, that corresponds to commit_v__hash; filled by prepare_vc_source
    vexename       string // v or v.exe
    vexepath       string // the full absolute path to the prepared v/v.exe
    vvlocation     string // v.v or compiler/ or cmd/v, depending on v version
    make_fresh_tcc bool   // whether to do 'make fresh_tcc' before compiling an old V.
    show_vccommit  bool   // show the V and VC commits, corresponding to the V commit-ish, that can be used to build V
}

pub fn (mut vgit_context VGitContext) compile_oldv_if_needed() {
    vgit_context.vexename = if os.user_os() == 'windows' { 'v.exe' } else { 'v' }
    vgit_context.vexepath = os.real_path(os.join_path_single(vgit_context.path_v,
        vgit_context.vexename))
    if os.is_dir(vgit_context.path_v) && os.is_executable(vgit_context.vexepath)
        && !vgit_context.show_vccommit {
        // already compiled, no need to compile that specific v executable again
        vgit_context.commit_v__hash = get_current_folder_commit_hash()
        return
    }
    scripting.chdir(vgit_context.workdir)
    clone_or_pull(vgit_context.v_repo_url, vgit_context.path_v)
    clone_or_pull(vgit_context.vc_repo_url, vgit_context.path_vc)
    scripting.chdir(vgit_context.path_v)
    scripting.frun('git checkout --quiet ${vgit_context.commit_v}') or {
        co_fail(err, vgit_context.commit_v)
    }
    if os.is_dir(vgit_context.path_v) && os.exists(vgit_context.vexepath)
        && !vgit_context.show_vccommit {
        // already compiled, so no need to compile v again
        vgit_context.commit_v__hash = get_current_folder_commit_hash()
        return
    }
    v_commithash, vccommit_before, v_timestamp := prepare_vc_source(vgit_context.path_vc,
        vgit_context.path_v, 'HEAD')
    vgit_context.commit_v__hash = v_commithash
    vgit_context.commit_v__ts = v_timestamp
    vgit_context.commit_vc_hash = vccommit_before

    if vgit_context.show_vccommit {
        println('VHASH=${vgit_context.commit_v__hash}')
        println('VCHASH=${vgit_context.commit_vc_hash}')
        exit(0)
    }

    if os.exists('cmd/v') {
        vgit_context.vvlocation = 'cmd/v'
    } else {
        vgit_context.vvlocation = if os.exists('v.v') { 'v.v' } else { 'compiler' }
    }
    if os.is_dir(vgit_context.path_v) && os.exists(vgit_context.vexepath) {
        // already compiled, so no need to compile v again
        return
    }

    scripting.chdir(vgit_context.path_v)
    // Recompilation is needed. Just to be sure, clean up everything first.
    scripting.run('git clean -xf')
    if vgit_context.make_fresh_tcc {
        scripting.run('make fresh_tcc')
    }

    // compiling the C sources with a C compiler:
    mut command_for_building_v_from_c_source := ''
    mut command_for_selfbuilding := ''
    mut c_flags := '-std=gnu11 -I ./thirdparty/stdatomic/nix -w'
    mut c_ldflags := '-lm -lpthread'
    mut vc_source_file_location := os.join_path_single(vgit_context.path_vc, 'v.c')
    mut vc_v_cpermissive_flags := '${vgit_context.cc_options} -Wno-error=incompatible-pointer-types -Wno-error=implicit-function-declaration -Wno-error=int-conversion -fpermissive'
    // after 85b58b0 2021-09-28, -no-parallel is supported, and can be used to force the cgen stage to be single threaded, which increases the chances of successful bootstraps
    mut vc_v_bootstrap_flags := ''
    if vgit_context.commit_v__ts >= 1632778086 {
        vc_v_bootstrap_flags += ' -no-parallel'
    }
    vc_v_bootstrap_flags = vc_v_bootstrap_flags.trim_space()
    scripting.verbose_trace(@FN, 'vc_v_bootstrap_flags: ${vc_v_bootstrap_flags}')
    scripting.verbose_trace(@FN, 'vc_v_cpermissive_flags: ${vc_v_cpermissive_flags}')
    scripting.verbose_trace(@FN, 'vgit_context.commit_v__ts: ${vgit_context.commit_v__ts}')

    if 'windows' == os.user_os() {
        c_flags = '-std=c99 -I ./thirdparty/stdatomic/win -w'
        c_ldflags = ''
        v_win_c_location := os.join_path_single(vgit_context.path_vc, 'v_win.c')
        if os.exists(v_win_c_location) {
            vc_source_file_location = v_win_c_location
        }
    }
    if 'windows' == os.user_os() {
        if vgit_context.commit_v__ts >= 1589793086 && vgit_context.cc.contains('gcc') {
            // after 53ffee1 2020-05-18, gcc builds on windows do need `-municode`
            c_flags += '-municode'
        }
        // after 2023-11-07, windows builds need linking to ws2_32:
        if vgit_context.commit_v__ts >= 1699341818 && !vgit_context.cc.contains('msvc') {
            c_flags += '-lws2_32'
        }
        command_for_building_v_from_c_source = c(vgit_context.cc,
            '${vc_v_cpermissive_flags} ${c_flags} -o cv.exe "${vc_source_file_location}" ${c_ldflags}')
        command_for_selfbuilding = c('.\\cv.exe',
            '${vc_v_bootstrap_flags} -cflags "${vc_v_cpermissive_flags}" -o ${vgit_context.vexename} {SOURCE}')
    } else {
        command_for_building_v_from_c_source = c(vgit_context.cc,
            '${vc_v_cpermissive_flags} ${c_flags} -o cv "${vc_source_file_location}" ${c_ldflags}')
        command_for_selfbuilding = c('./cv',
            '${vc_v_bootstrap_flags} -cflags "${vc_v_cpermissive_flags}" -o ${vgit_context.vexename} {SOURCE}')
    }

    scripting.run(command_for_building_v_from_c_source)
    build_cmd := command_for_selfbuilding.replace('{SOURCE}', vgit_context.vvlocation)
    scripting.run(build_cmd)
    // At this point, there exists a file vgit_context.vexepath
    // which should be a valid working V executable.
}

fn c(cmd string, params string) string {
    // compose a command, while reducing the potential whitespaces, due to all the interpolations of optional flags above
    return '${cmd} ${params.trim_space()}'
}

pub struct VGitOptions {
pub mut:
    workdir     string = os.temp_dir() // the working folder (typically /tmp), where the tool will write
    v_repo_url  string // the url of the V repository. It can be a local folder path, if you want to eliminate network operations...
    vc_repo_url string // the url of the vc repository. It can be a local folder path, if you want to eliminate network operations...
    show_help   bool   // whether to show the usage screen
    verbose     bool   // should the tool be much more verbose
}

pub fn add_common_tool_options(mut context VGitOptions, mut fp flag.FlagParser) []string {
    context.workdir = os.real_path(fp.string('workdir', `w`, context.workdir,
        'A writable base folder. Default: ${context.workdir}'))
    context.v_repo_url = fp.string('vrepo', 0, context.v_repo_url,
        'The url of the V repository. You can clone it locally too. See also --vcrepo below.')
    context.vc_repo_url = fp.string('vcrepo', 0, context.vc_repo_url, 'The url of the vc repository. You can clone it
${flag.space}beforehand, and then just give the local folder
${flag.space}path here. That will eliminate the network ops
${flag.space}done by this tool, which is useful, if you want
${flag.space}to script it/run it in a restrictive vps/docker.
')
    context.show_help = fp.bool('help', `h`, false, 'Show this help screen.')
    context.verbose = fp.bool('verbose', `v`, false, 'Be more verbose.')
    if context.show_help {
        println(fp.usage())
        exit(0)
    }
    if context.verbose {
        scripting.set_verbose(true)
    }
    if os.is_dir(context.v_repo_url) {
        context.v_repo_url = os.real_path(context.v_repo_url)
    }
    if os.is_dir(context.vc_repo_url) {
        context.vc_repo_url = os.real_path(context.vc_repo_url)
    }
    commits := fp.finalize() or {
        eprintln('Error: ${err}')
        exit(1)
    }
    for commit in commits {
        validate_commit_exists(commit)
    }
    return commits
}