#!/bin/sh

# Copyright (c) 2016, Antonio SJ Musumeci <trapexit@spawn.link>

# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.

# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

# Default values
NAME=""
VERSION="::guess::"
DISTRO="::guess::"
CODENAME="::guess::"
URGENCY="medium"

# Function to display usage
usage() {
    cat << EOF
Usage: $0 --name NAME [OPTIONS]

Generated debian/changelog from git log

Options:
    --name NAME        Name of package (required)
    --version VERSION  Place in git history to include upto (default: ::guess::)
    --distro DISTRO    Distribution name (default: ::guess::)
    --codename NAME    Distribution codename (default: ::guess::)
    --urgency URGENCY  Urgency (default: medium)
    -h, --help         Show this help message
EOF
    exit 1
}

# Parse command line arguments
while [ $# -gt 0 ]; do
    case "$1" in
        --name)
            NAME="$2"
            shift 2
            ;;
        --version)
            VERSION="$2"
            shift 2
            ;;
        --distro)
            DISTRO="$2"
            shift 2
            ;;
        --codename)
            CODENAME="$2"
            shift 2
            ;;
        --urgency)
            URGENCY="$2"
            shift 2
            ;;
        -h|--help)
            usage
            ;;
        *)
            echo "Unknown option: $1" >&2
            usage
            ;;
    esac
done

# Check required arguments
if [ -z "$NAME" ]; then
    echo "Error: --name is required" >&2
    usage
fi

# Function to get git tags sorted in reverse order
git_tags() {
    git tag -l | sort -rV
}

# Function to get git log between two tags
git_log() {
    local fromtag="$1"
    local totag="$2"
    git log --no-merges --oneline "${fromtag}...${totag}" 2>/dev/null
}

# Function to get author and time for a tag
git_author_and_time() {
    local tag="$1"
    git log -1 --format="-- %an <%ae>  %cD" "$tag"
}

# Function to get git version
git_version() {
    git describe --always --tags --dirty 2>/dev/null || echo "unknown"
}

# Function to guess distribution
guess_distro() {
    if command -v lsb_release >/dev/null 2>&1; then
        lsb_release -i -s 2>/dev/null | tr '[:upper:]' '[:lower:]'
    else
        echo "unknown"
    fi
}

# Function to guess codename
guess_codename() {
    if command -v lsb_release >/dev/null 2>&1; then
        lsb_release -c -s 2>/dev/null | tr '[:upper:]' '[:lower:]'
    else
        echo "unknown"
    fi
}

# Handle guessing of values
if [ "$DISTRO" = "::guess::" ]; then
    DISTRO=$(guess_distro)
fi

if [ "$CODENAME" = "::guess::" ]; then
    CODENAME=$(guess_codename)
fi

if [ "$VERSION" = "::guess::" ]; then
    VERSION=$(git_version)
fi

# Version suffix
VERSUFFIX="~${DISTRO}-${CODENAME}"

# Get all tags
TAGS=$(git_tags)

# Create temporary file for tag pairs
TMPFILE=$(mktemp)
trap 'rm -f "$TMPFILE"' EXIT

# Check if version is in tags
if echo "$TAGS" | grep -q "^${VERSION}$"; then
    # If version is a tag, start from that tag
    echo "$TAGS" | awk -v ver="$VERSION" 'BEGIN{found=0} {if($0==ver)found=1; if(found)print}' > "$TMPFILE"
else
    # If version is not a tag, use HEAD as starting point
    echo "$VERSION HEAD" > "$TMPFILE"
    echo "$TAGS" >> "$TMPFILE"
fi

# Process tags and generate changelog
PREV_TAG=""
PREV_REF=""
FIRST=1

while IFS= read -r line; do
    if [ -z "$line" ]; then
        continue
    fi
    
    # Handle the special case of VERSION HEAD
    if [ "$line" = "$VERSION HEAD" ]; then
        TAG="$VERSION"
        REF="HEAD"
    else
        TAG="$line"
        REF="$line"
    fi
    
    if [ -n "$PREV_TAG" ]; then
        # Get log entries between current and previous tag
        LOG_ENTRIES=$(git_log "$REF" "$PREV_REF")
        
        # Skip if no changes
        if [ -z "$LOG_ENTRIES" ] || [ "$LOG_ENTRIES" = "" ]; then
            PREV_TAG="$TAG"
            PREV_REF="$REF"
            continue
        fi
        
        # Print package header
        printf "%s (%s%s) %s; urgency=%s\n\n" "$NAME" "$PREV_TAG" "$VERSUFFIX" "$CODENAME" "$URGENCY"
        
        # Print each log entry
        echo "$LOG_ENTRIES" | while IFS= read -r entry; do
            if [ -n "$entry" ]; then
                printf "  * %s\n" "$entry"
            fi
        done
        
        # Print author and time
        AUTHOR_TIME=$(git_author_and_time "$PREV_REF")
        printf "\n %s\n\n" "$AUTHOR_TIME"
    fi
    
    PREV_TAG="$TAG"
    PREV_REF="$REF"
done < "$TMPFILE"