#!/bin/zsh
#set -x
set -euo pipefail
export GO111MODULE=on
export GOPATH="$(go env GOPATH)"

alias jq="jq --unbuffered"

[[ -n "${REPO_FILTER+x}" ]] || REPO_FILTER="github.com/(ipfs|libp2p|ipld)"
[[ -n "${IGNORED_FILES+x}" ]] || IGNORED_FILES='^\(\.gx\|package.json\|\.travis.yml\|go.mod\|go.sum\)$'

NL=$'\n'

msg() {
    echo "$*" >&2
}

statlog() {
    rpath="$GOPATH/src/$1"
    start="${2:-}"
    end="${3:-HEAD}"
    git -C "$rpath" log --shortstat --no-merges --pretty="tformat:%H%n%aN%n%aE" "$start..$end" | while 
        read hash
        read name
        read email
        read _ # empty line
        read changes
    do
        changed=0
        insertions=0
        deletions=0
        while read count event; do
            if [[ "$event" =~ ^file ]]; then
                changed=$count
            elif [[ "$event" =~ ^insertion ]]; then
                insertions=$count
            elif [[ "$event" =~ ^deletion ]]; then
                deletions=$count
            else
                echo "unknown event $event" >&2
                exit 1
            fi
        done<<<"${changes//,/$NL}"

        jq -n \
           --arg "hash" "$hash" \
           --arg "name" "$name" \
           --arg "email" "$email" \
           --argjson "changed" "$changed" \
           --argjson "insertions" "$insertions" \
           --argjson "deletions" "$deletions" \
           '{Commit: $hash, Author: $name, Email: $email, Files: $changed, Insertions: $insertions, Deletions: $deletions}'
    done
}

# Returns a stream of deps changed between $1 and $2.
dep_changes() {
    {
        <"$1"
        <"$2"
    } | jq -s 'JOIN(INDEX(.[0][]; .Path); .[1][]; .Path; {Path: .[0].Path, Old: (.[1] | del(.Path)), New: (.[0] | del(.Path))}) | select(.New.Version != .Old.Version)'
}

# resolve_commits resolves a git ref for each version.
resolve_commits() {
    jq '. + {Ref: (.Version|capture("^((?<ref1>.*)\\+incompatible|v.*-[0-9]{14}-(?<ref2>[a-f0-9]{12})|(?<ref3>v.*))$") | .ref1 // .ref2 // .ref3)}'
}

# Generate a release log for a range of commits in a single repo.
release_log() {
    local repo="$1"
    local start="$2"
    local end="${3:-HEAD}"
    local ghname="${repo##github.com/}"
    local dir="$GOPATH/src/$repo"

    local commit prnum
    git -C "$dir" log \
        --format='tformat:%H %s' \
        --merges \
        "$start..$end" |
        sed -n -e 's/\([a-f0-9]\+\) .*#\([0-9]\+\).*/\1 \2/p' |
        while read commit prnum; do
            # Skip gx-only PRs.
            git -C "$dir" diff-tree --no-commit-id --name-only "$commit^" "$commit" |
                grep -v "${IGNORED_FILES}" >/dev/null || continue

            local desc="$(git -C "$dir" show --summary --format='tformat:%b' "$commit" | head -1)"
            printf -- "- %s ([%s#%s](https://%s/pull/%s))\n" "$desc" "$ghname" "$prnum" "$repo" "$prnum"
        done
}

indent() {
    sed -e 's/^/  /'
}

mod_deps() {
    go list -json -m all | jq 'select(.Version != null)'
}

ensure() {
    local repo="$1"
    local commit="$2"
    local rpath="$GOPATH/src/$repo"
    if [[ ! -d "$rpath" ]]; then
        msg "Cloning $repo..."
        git clone "http://$repo" "$rpath" >&2
    fi

    if ! git -C "$rpath" rev-parse --verify "$commit" >/dev/null; then
        msg "Fetching $repo..."
        git -C "$rpath" fetch --all >&2
    fi

    git -C "$rpath" rev-parse --verify "$commit" >/dev/null || return 1
}

statsummary() {
    jq -s 'group_by(.Author)[] | {Author: .[0].Author, Commits: (. | length), Insertions: (map(.Insertions) | add), Deletions: (map(.Deletions) | add), Files: (map(.Files) | add)}' |
        jq '. + {Lines: (.Deletions + .Insertions)}'
}

recursive_release_log() {
    local start="${1:-$(git tag -l | sort -V | grep -v -- '-rc' | grep 'v'| tail -n1)}"
    local end="${2:-$(git rev-parse HEAD)}"
    local repo_root="$(git rev-parse --show-toplevel)"
    local package="$(go list)"
    (
        local workspace="$(mktemp -d)"
        trap "$(printf 'rm -rf "%q"' "$workspace")" INT TERM EXIT
        cd "$workspace"

        echo "Computing old deps..." >&2
        git -C "$repo_root" show "$start:go.mod" >go.mod
        mod_deps | resolve_commits | jq -s > old_deps.json

        echo "Computing new deps..." >&2
        git -C "$repo_root" show "$end:go.mod" >go.mod
        mod_deps | resolve_commits | jq -s > new_deps.json

        rm -f go.mod go.sum

        printf -- "Generating Changelog for %s %s..%s\n" "$package" "$start" "$end" >&2

        printf -- "- %s:\n" "$package"
        release_log "$package" "$start" "$end" | indent


        statlog "$package" "$start" "$end" > statlog.json

        dep_changes old_deps.json new_deps.json |
            jq --arg filter "$REPO_FILTER" 'select(.Path | match($filter))' |
            # Compute changelogs
            jq -r '"\(.Path) \(.New.Version) \(.New.Ref) \(.Old.Version) \(.Old.Ref // "")"' |
            while read repo new new_ref old old_ref; do
                ensure "$repo" "$new_ref"
                statlog "$repo" "$old_ref" "$new_ref" >> statlog.json
                local changelog="$(release_log "$repo" "$old_ref" "$new_ref")"
                if [[ -n "$changelog" ]]; then
                    printf -- "- %s (%s -> %s):\n" "$repo" "$old" "$new"
                    echo "$changelog" | indent
                fi
            done

        echo
        echo "Contributors"
        echo

        echo "| Contributor | Commits | Lines ± | Files Changed |"
        echo "|-------------|---------|---------|---------------|"
        statsummary <statlog.json |
            jq -s 'sort_by(.Lines) | reverse | .[]' |
            jq -r '"| \(.Author) | \(.Commits) | +\(.Insertions)/-\(.Deletions) | \(.Files) |"'
    )
}

recursive_release_log "$@"
